Background: bio-parents divorced in oct 2007, bio-dad and I got together in nov of 07. The kid liked me from the start, I have a baby girl and he loved to go places with us.

Now the kid hates me, he doesn't listen to me at all. He will sit there and ignore everything I tell him to do, especially like picking his nose, scratching his butt in the grocery store, flushing the toilet and putting the seat down.
I think he does these things just to be a Sh**head. His mother hates me, she didn't at first because she was getting some from some creepy guy who abused my SS repeatedly before we realized it and pressed charges. Now this kid is with me everyday, and he doesn't like me so tries his best to get me to leave which I am not going to do.
I hate trying to talk to his dad about him, it seems like everyone is in denial that there is a problem with this kid. He threatened to shoot his aunt and uncle the other day. he's in counseling, he has no friends because no one can stand to be around the kid. He hates his teachers because he gets punished for acting like a two year old at school. He hates me because I punish him for acting like a two year old (throwing temper tantrums, pooing in his pants, picking his nose, walking around naked, throwing toys at the walls). Apparently his mother never punishes him, because when anyone does-he hates them and treats them like S**t.

Am I wrong to believe that a 7 year old should act seven (I am a senior psychology major, so I know what 7 year olds should act like)?
Do I have a right to take things away from him when he starts breaking things?
Should I cater to him like his mother does?
I believe that in order to love a child, that child needs to have discipline consistently, if a parent doesn't take the time to discipline their child, they can't possibly love it.