I apologize for how clunky it is.
if(not empty(prop("Recur Interval")) and not empty(prop("Due")), if(prop("Recur Interval") > 0 and prop("Recur Interval") == ceil(prop("Recur Interval")), formatDate(if(length(prop("Days (Only if Set to 1 Day(s))")) > 0 and prop("Recur Unit") == "Day(s)" and prop("Recur Interval") == 1, if(dateBetween(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, if(test(format(prop("Due")), "AM|PM"), now(), dateAdd(now(), prop("UTC Offset"), "hours")), now()), now()), prop("Due"), "days") >= 1 and unequal(formatDate(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), "MMMM D, YYYY"), formatDate(prop("Due"), "MMMM D, YYYY")), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 1, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 1, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 2, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 2, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 3, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 3, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 4, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 4, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 5, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 5, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 6, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 6, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 7, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), 7, "days"), fromTimestamp(9.07002e+11)))))))), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(prop("Due"), 1, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(prop("Due"), 1, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(prop("Due"), 2, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(prop("Due"), 2, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(prop("Due"), 3, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(prop("Due"), 3, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(prop("Due"), 4, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(prop("Due"), 4, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(prop("Due"), 5, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(prop("Due"), 5, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(prop("Due"), 6, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(prop("Due"), 6, "days"), if(length(replaceAll(replaceAll(prop("Days (Only if Set to 1 Day(s))"), formatDate(dateAdd(prop("Due"), 7, "days"), "dddd"), "§"), "[^§]", "")) > 0, dateAdd(prop("Due"), 7, "days"), fromTimestamp(9.07002e+11))))))))), if(prop("Recur Unit") == "Month(s) on the Last Day", prop("Last Day Base Date"), if(prop("Recur Unit") == "Month(s) on the Last Weekday", if(dateBetween(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, if(test(format(prop("Due")), "AM|PM"), now(), dateAdd(now(), prop("UTC Offset"), "hours")), now()), now()), prop("Last Weekday Base Date"), "days") >= 1 or equal(formatDate(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), "L"), formatDate(prop("Last Weekday Base Date"), "L")), if(day(prop("Next Last Base Date")) == 0, dateSubtract(prop("Next Last Base Date"), 2, "days"), if(day(prop("Next Last Base Date")) == 6, dateSubtract(prop("Next Last Base Date"), 1, "days"), prop("Next Last Base Date"))), prop("Last Weekday Base Date")), if(prop("Recur Unit") == "Month(s) on the First Weekday", if(dateBetween(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, if(test(format(prop("Due")), "AM|PM"), now(), dateAdd(now(), prop("UTC Offset"), "hours")), now()), now()), prop("First Weekday Base Date"), "days") >= 1 or equal(formatDate(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), "L"), formatDate(prop("First Weekday Base Date"), "L")), if(day(dateSubtract(prop("Next Last Base Date"), date(prop("Next Last Base Date")) - 1, "days")) == 0, dateSubtract(prop("Next Last Base Date"), date(prop("Next Last Base Date")) - 2, "days"), if(day(dateSubtract(prop("Next Last Base Date"), date(prop("Next Last Base Date")) - 1, "days")) == 6, dateSubtract(prop("Next Last Base Date"), date(prop("Next Last Base Date")) - 3, "days"), dateSubtract(prop("Next Last Base Date"), date(prop("Next Last Base Date")) - 1, "days"))), prop("First Weekday Base Date")), if(dateBetween(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, if(test(format(prop("Due")), "AM|PM"), now(), dateAdd(now(), prop("UTC Offset"), "hours")), now()), now()), prop("Due"), "days") >= 1 and unequal(formatDate(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, dateAdd(now(), prop("UTC Offset"), "hours"), now()), now()), "L"), formatDate(prop("Due"), "L")), if(equal(dateBetween(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, if(test(format(prop("Due")), "AM|PM"), now(), dateAdd(now(), prop("UTC Offset"), "hours")), now()), now()), prop("Due"), prop("Simplified Recur Unit")) / prop("Recur Interval"), ceil(dateBetween(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, if(test(format(prop("Due")), "AM|PM"), now(), dateAdd(now(), prop("UTC Offset"), "hours")), now()), now()), prop("Due"), prop("Simplified Recur Unit")) / prop("Recur Interval"))), dateAdd(prop("Due"), multiply(dateBetween(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, if(test(format(prop("Due")), "AM|PM"), now(), dateAdd(now(), prop("UTC Offset"), "hours")), now()), now()), prop("Due"), prop("Simplified Recur Unit")) / prop("Recur Interval") + 1, prop("Recur Interval")), prop("Simplified Recur Unit")), dateAdd(prop("Due"), multiply(ceil(dateBetween(if(formatDate(now(), "z") == "UTC", if(not empty(prop("UTC Offset")) and prop("UTC Offset") >= -12 and prop("UTC Offset") <= 14, if(test(format(prop("Due")), "AM|PM"), now(), dateAdd(now(), prop("UTC Offset"), "hours")), now()), now()), prop("Due"), prop("Simplified Recur Unit")) / prop("Recur Interval")), prop("Recur Interval")), prop("Simplified Recur Unit"))), dateAdd(prop("Due"), prop("Recur Interval"), prop("Simplified Recur Unit"))))))), "MMMM D, YYYY"), "Error in Recur Interval: Non-Whole or Negative Number"), "")
