What movie did i see as a kid?
 

So I have watched Phantasm and many other old 80/90s horror flicks trying to figure this one out, but still can't place it can you help me out?

The first thing I remember is there being a preteen boy and maybe his dad, they had stocked up to kill whatever they were hunting, presumably the main bad guy in the flick. I remember they open a door and a young blonde girl with no clothes on is on her knees hunched over crying on the floor, she looks up and say "help me". It is obviously someone the boy knows from school, maybe his girlfriend? Then her spine separates from her tailbone and a little monster skull lifts out and growls at them, the two torch the girl with a flamethrower. and that's it.

The only reason I thought it might have been phantasm is I though I also remember them being in a church with demons in brown coats shuffling around, and they are trying to avoid getting caught. Still can't figure it out. Help please!!!

Sounds like PHANTASM 2.