Sorry, a few comments:
Dante does 80 damage on a single body part (seemingly determined at random); this is new.
Purification grenade works like before: it does 20 blast damage and 5 shred, thus affecting several body parts (same as all explosives).
The fire status effect is removed after spending a whole turn without starting or stepping on a lit tile. Example: you start turn outside of fire. You run through a lit tile (acquiring fire status equal to the strength of the fire on the tile and taking immediate damage for stepping on a lit tile), but end your turn on a tile without fire. Next turn you will take damage from the status fire, but if you stay out of fire that entire turn, you will lose the fire status.
As you say, It’s not a bug, it’s just that diagonal movement in PP is possible and you only take damage from a lit tile if you step on it.
Please see above. I would describe it as
the target inherits the fire status of the tile it steps on, and fire status is lost after spending one turn outside of fire
I have specifically checked this: damage is taken for every lit tile that the target enters.