I really could use LOTS of advice here please!!

SS moved in with us (BD, me, BD(7), BS(4) and BS(3)) full time as of August 2010 due to his mother getting a divorce from her 2nd husband - who was my stepson's stepdad. Slight background here...SS's bio mother seperated from his bio dad when he was 4 and immediatly moved in with his soon to be stepdad (bio mom was having fun on the side). The new step dad had already had a daughter SS's age. I then met my husband not long after and got married and had our three kids. Fast forward to last summer, SS's bio mother had some more fun with her next door neighbor (who also has a daughter, age 9) and divorced. Bio mother moved in with next door neighbor but sent SS to live with us saying she could not afford him(true even with support)and the new man in her life does not like SS. Needless to say, my SS probably has issues with his mother.

My problem started a few months after he moved in with us full time, At first I was excited to have him here full time so he could connect more with his half-siblings and maybe he could see what a stable and happy home life could be. I am a SAHM and after witnessing months of interaction between all of the kids I have found that he acts nice and understanding when and adult is present but entirely different when alone with the kids. My daughter(7) has repetedly told me that SS is hitting,putting his hands around her throat and kicking. At first I did not believe it because I did not see any marks on her body, my daughter can exaggerate a bit at times and SS is a very accomplished liar. This stopped when I witnessed my SS kicking my daughter in the back after she was trying to lean up against him while watching tv. I flew off the handle at him. Now that I actually saw SS physically harming her I am more vigilant. A couple weeks ago my daughterr started crying all of a sudden and said SS kicked her again(I was in the next room). This time there was a red mark exactly where she said he kicked her. Husband came home and had a discussion with him and SS admitted that most of the times my daughter has said he hurt her was true. There has also been time where my daughter has said SS says he hates her etc.

Compile this with SS's GPA of 1.2 (should be entering his senior year but looks like he still does not have enough credits to pass sophmore year), does not complete chores at all, lies constantly and have caught him wandering in my bedroom with no good reason. What I really love is when he had a few friends over some time ago, I took my kids in the basement so SS could have time alone with friends. He then locked the basement door, locking me down there with the kids. Luckily it is a walkout so I went out the basement, around the house and in through the front door. Where was SS? Found him in the house with one of his friends by the basement door looking guilty. No excuse for locking the door.

My husband is at his wits end and told his son he will need to live with his grandparents in another state but is having second thoughts. Husband keeps saying he does not want to give up on his son. I can understand this but at the same time cannot trust SS alone with my daughter. Husband wants to know what I want to do.

I want to kid gone, out of my home but feel as a stepparent I should not vocalize this. On the other hand, it is just one more year until he turns 18. Tried counseling too. Please I need opinions from other stepparents!!!!