hi J. ((((hugs))))
they don't always respond to what they see. i'm a single parent of one boy (now 7) and when he was 3, 4, 5, he did the same things. he still does! but back then, he wasn't in school, we've never had cable, i picked our friends very carefully...and yet, he still made guns out of toast (lol whitney!).
i stumbled upon a book called "who's calling the shots?" and it was very illuminating. it was originally (if i remember correctly) a thesis paper that ended up being published. it addressed child's play, and how it's changed since it's been legal to tie in toys with TV shows and movies. but it also goes into how boys and girls are differently wired, etc.
i used to ban guns and gun play. i find it super disturbing. my ds goes around even now saying "i LOVE violence"-- talk about creepy. but he does show plenty of compassion so i'm not worried. he turns his face away from "real" violence in the movies. in spider-man when the uncle gets hit by a car and there's blood in his mouth, my ds can't even watch that. he turns his whole body away, not just his face!
but i don't ban that kind of play anymore. apparently it gets out some sort of stress, or whatever. i just make him go outside where i can't see or hear it, and i check on him visually through the window :-)
as for the peeing, i would check at school-- maybe he's being bullied. maybe he's acting out. i wouldn't stress in front of him or question him too much; it might make it worse.
OH, and the ick language at the table-- for me, i would tell him that "we use polite language at the table" and maybe demonstrate what conversation is about, ie "what was your favorite part of the day?", and if he can't get that, send him away from the table. as for the rest of the house, i'd say "you can talk like that by yourself where nobody can hear you, but i don't like to hear it, and there will be consequenses, so you need to remember". you'll have to fit your own consequenses for whatever works in your family.
good luck! i highly recommend that book. i bet you can find it on www.half.com for a reasonable price.
P.