Why does being on fire seem to have so little effect? Anything on fire, except robots and maybe ghouls, should have a high chance of running away or rolling around on the ground to put themselves out.

Not sure if ghouls or robots were taught fire safety

Yes. Stop, drop and roll might be a tad difficult for a Mr Handy.

Duck and cover.

If you haven't get awareness. In vats It shows how much armor they have against different damage types and thier level. I have armor that gives me immunity against fire.