Looks like I solved the problem, and it was caused by something related to what I had assumed was the cause.
I duplicated the defaulttextmaterial asset to try and make a new text render material with a new font. During this process I had to import the font with some specific settings that were unusual to me. I followed this step by step guide:
I did the same thing in a blank project without issue, but I believe I somehow corrupted the font texture file in my original project when I was playing around with all of the font sheet texture settings to try and make it look clean. So whatever I did with that file specifically must have caused a problem with the engine startup routine.
I suspected this file was the problem, so reluctantly I removed it from my project folder using Windows Explorer, which I know can be dangerous but nothing else had worked. This allowed me to launch the editor and now it works just fine.
So I solved my issue, and if anyone comes across anything similar in the future I hope my solution can be helpful to them.