Lots going on here, but in my view, if he has been verbally and physically abusive since a young age, he has been looking for you to control him for a long time. It sounds like you are scared of him and have been since he was small- probably to do with the abuse you suffered from his father. The lack of you putting him in his proper place when he was young, probably feels to him like a lack of love - a bit like dominating a puppy to show him his proper place in the pack. Looking at it from his point of view, you didn't love him enough to keep him (I know that you probably feel very differently). Part of what he is doing is normal teenage behaviour, but part of it is testing you to see if you love him after all and as he is now in foster care, he probably feels that you have failed him.
I know that your own issues have prevented you from dealing with him earlier, this is not meant to sound like critisism, I am just trying to see it from his perspective. Children honestly like to have boundarys and to know that the grown ups are in charge, it makes them feel secure and loved. He has always had too much power over you.
You need to sit down with him and expain what happened with his dad and that it isn't his fault and that you love him for him, he is not his dad, he is not a freak and that you know that he is good person and that you want to be proud of him but what he is doing is not acceptable and that you wont have it in your house.
I wish you both the very best and hope you get the help you both need.