The barrel is what "takes" the pressure on firing. If the barrel is okay the other parts should be "safe" to use.
I've personally "baked" a rifle (FAL) at 550 F for 30 minutes to heat set/treat a ceramic finish on it. The rifle has had hundreds of rounds fired through it since then with no issues (its really pretty/nice looking now vs. prior to refinishing with the ceramic paint). If 550 F didn't hurt a .308 chamber I can't see 400 F hurting a .45 acp chamber. But I'm not an expert.
Are you sure the slide is hung up due to frame warpage?
If it were mine I'd soak it in some oil for a few days. If the slide still won't move I get a rubber mallet or soft faced mallet (polyester/urethane heads) and try to tap the slide to the rear with the frame clamped in a padded vise. If the frame is warmped the slide should still move back (with help from the mallet/hammer) and you should be able to stop it where it lines up with the slide stop. If the spring pops the slide back forward then its not hanging up on the frame right now.
If you can get the slide back enough to get the slide stop out then tap the slide forward with the hammer/mallet till you get it off.
I'd take all the parts out of the frame (new springs need to be installed anyway) and then just use the vise, or a press, to try to slightly, a little at a time, "unswell" the frame/rails. I wouldn't use any heat on it. There's really no in/out stress on a frame anyway. You just need the rails straight enough for the slide to move and straight enough that any wear is even along the length of the rails on the frame and slide.
it would be a fun/interesting project to tinker with.
I used to dry my Ruger speed six in the oven after fisihing trips because it almost always got submerged for some period of time while wading the river small mouth bass fishing. I never used temperatures over 200 F and it was only in there long enough for me to take a shower before work. I'd unload it, take it apart (Speed Sixes come apart very quickly/easily - its a modular design), put it on a cookie pan and "dry it out". When I got out of the shower I'd pull it out of the over to cool while I got dressed. Then I'd wipe it down, lube it up and put it back together before loading it up and dropping it in my pocket to walk to work.
Good memories, good days.
Good luck with your "little project".