If you save a game while you have Pyro Field active and reload it, the light emenating from your character will remain for the duration of the game for that particular level. I've tried reloading or going to new areas but the light will always be there when I return to the area.

yes, a bug old as the game itself.

also, toilets burned by the pyro field scream.

Also computer consoles burned by the Pyro Field grunt! :P

and you are immune to protocol droids exploding.

hard to tell. the fire field also absorbing all fire damage does sound plausible, and without this, the pyro field would be quite useless.

It's a consequence of how Dark handles damage. The player is set to be immune to fire damage while the ability is active, else you'd burn yourself to a crisp when using the ability, as well as enemies, toilets and the like. Some explosions as well as projected pyrokinesis do fire damage, hence if you have pyro field active you're immune to those as well.