Re: the broken character stats stuff. In TSF, I remember some should-be temporary boosts (Potion of Giant Strength and Potion of Spell Enhancement) beeing permanent. This can simply be fixed by deleting (make backups!) of the .EFX file(s) from the savegame as needed. Of course, all other temporary effects will be gone to, and some items might need to be re-readied.
The following I think isn't widely known, because it only comes with the later games; I think it's been there since POD. The temples have been added with an aptly named REPAIR function, which I guess was meant as a feature of convenience, like the FIX command. I noticed that using the REPAIR command, sometimes raises some characters HP. Permanently.
More recently, I noticed this in TSF with a Dwarf Fighter/Thief with 19 CON. I like to save scum to get max HP per level up (or I can't resist the compulsion to not do so); with 19 CON, a 2-class character should get 7.5 HP/level of fighter, which from experience always get rounded down to 7 HP. On one occasion, I noticed the tiny, but permanent increase of 1 HP when using REPAIR on a respective dwarven PC. I explained this to me as retroactively gaining 2*0.5 HP from past level-ups. The respective PC was never drained, which I'm mentioning because of the following.
Ages ago in POD, I had several PCs which had been drained in the course of the adventure once or several times. I usually
fixed repaired took care of this manually by casting Restoration as needed (which the FIX command doesn't get straight AFAIR). Then on some occasion, I curiously tried REPAIR in a temple on a (from my perspective) fully healthy party, and was surprised by a notable increase of HP on some PCs (can't remember exact numbers, but a Paladin ~level 30 with 218 HP @ CON 18). I figured this was an after-effect of level draining.
Which lead me to dislike level draining even more so than before. I like optimized characters, but not broken characters. Until today, when one of my PCs (don't care enough for NPCs...) gets hit by a level draining monster, I immediately quit the game and reload. I KNOW that I don't NEED to use REPAIR, but on the other hand just KNOWING that a PC might be gimped...