I am no super-genius, the fact that I can code in c++ and made a mod is probably a minor miracle. After looking at the map for a few minutes for absolutely anything wrong, I could find nothing that could throw an exception as severe as the one it gave me. That threw me into a panic thinking about possibly compatibility issues arising from PolyObjects, the most common culprit in ZDoom mod crashes that use them. Well I went out for the day and did my thing, then came home and took one last look at it before attempting to salvage a broken project. One thing, something that was almost too stupid to have occured, there was no player start spot!
Normally, ZDoom would just give you a kind error saying that there is no start spot. The rather dramatically worded ZDoom exception screen it threw at me was unusual, so not remembering to put in a start spot didn't cross my mind.
Regardless! Everything is back on track and providing I do not forget to put in start spots, progress will be made!