As to the crashing when leaving Toxic Caves, it doesn't matter if I do anything at all there. This happens to me in every new game I start. I just save before trying to leave, and keep trying, eventually it works. This also happens to me when I enter inner Vault City (map2), and whenever I try to enter Klamath after game completion. It's irritating, but seems to work itself out. I can't seem to force these crashes or avoid them, just randomly happens, maybe we are pushing Fallout2 past it's maximum ability.
I have been doing a lot of testing with Klint, and the only time he gives me problems is if I equip him with a Mark 2 armor, Hardened PA, or Advanced PA (Mark 1 or 2). Otherwise I haven't been able to replicate any problems anyone else has had with him. After giving him a Mark 2 armor, just ask him to remove armor, then you can trade it for something else, and he is completely ok. Maybe he got fixed in the last update.
Any time I try to enter under Carson City I get a black screen that gives repeating cursor images everywhere. It happens in other places sometimes, usually fixed by quitting FO2 and loading game prior to entring area with error. Never worked under Carson.
After game completion, I can no longer choose to enter combat with mantis or roaches random encounters. I say yes to encounter and then continue moving on map as if nothing happened. I haven't had it happen to other encounters than those yet.
Also after game completion, attempting to use Mr. Fixit causes CTD, always.
EDIT: Added Mr. Fixit error.