dozens of error reports every step. Can I turn them off?

[Coldbringer]

I think your hunch was correct! I went back up to a previous floor in Dreadfell and now I can move around freely without any error reports popping up. I imagine the error flood will resume as soon as I go back down to that level again.

IIRC, it might have something to do with an escort. One of the mods (that I've disabled months ago), I think it was "choose your escorts" bugged escorts so that they wouldn't even appear on levels they were supposed to and an error report popped up instead as soon as I entered the level. There's an escort portal on the floor where the error reports were flooding the screen. Maybe that has nothing to do with it, I don't know.

[HousePet]

At least one of the critters on that floor has an active timed effect that no longer links to any code. Since it doesn't have the code it isn't going to time out eventually either.
Your options are to run through the floor as fast as possible, or hope you can find and kill the critter.
If it was a less plot relevant dungeon, I would suggest forcing a regeneration. But that would be an extremely bad idea for Dreadfell.

[St_ranger_er]

As HousePet said, skipping level by TP'ing to the next one manually around the map to stairs(ctrl + click I believe) or through ctrl + a menu might be best option, if it wasn't final level.