Total word on the "..." stuff. Unless you're writing a script-style fic (which, I'll be honest, usually doesn't work for me), use some description, damn it.

I think "cum" is supposed to be slang for ejaculate. If it's used for anything else, though, yeah, it's just bad spelling.

You know what I can't stand in smut? The word "juice." If it's not coming out of a carton I can buy at a grocery store, it's not juice and I don't want that word in my porn, kthnks. (Ignoring the fact that I don't really get why people are so fascinated with semen and vaginal secretions getting everywhere. IMO it's not at all sexy.)