On my first visit of the game to Goat City I entered the Goat Temple. But whenever I try to leave, I get errors like these. Is there like a line I could type into the debugging console that would just teleport me to Goat City Proper?

An educated guess is your savegame has been corrupted. You should be able to fix it by going into your most recent save and removing 20_GoatCity.dxs from the folder. Don't delete it though, just move it somewhere else, just in case. If it works, then you can delete it after checking. This has the side effect of resetting any changes you've made to the Goat City level, reviving any non-critical character you've killed and respawning any item you've picked up, relocking doors you've picked etc.

My concern is that judging from your error message, it may be the Goat Templae level that's fucked up, which is where you made the save, right? In that case you could be out of luck, and you may have to go back to an earlier save. In that case, I'm sorry

If you'd like to try to teleport yourself to Goat City before doing anything else, the command is "travel 20_goatcity" without the quotes.

Yep, the save is in the Temple. And trying to teleport causes the same crash and error. I don't suppose there's anyway out of this? Thanks for taking the time to reply though.

Does using the "ghost" cheat cause a crash too?

Noclipping won't get me out of the area, but no, it doesn't crash it. From an old save, teleporting to Goat City, entering the temple, and leaving cause no problems. But in that save I can't uncrouch.

If the save were corrupted, I shouldn't be able to load it at all, right? It's just that I can't leave the area, either on foot or via cheats. I can't help but think this must have been caused by listening to that sermon or taking certain items from the area.

Well did you try removing the Goat City map from your savegame folder? That shouldn't undo too much of your progress, assuming it works.