hay moma. You have really put yourself in a difficult situation.. It's a battle dealing with teens/preteens when there yours let alone when there your spouses. I have a few issues with my step daughter but that's a whole other thread. I was raised in a house hold with a step dad since I was 2yrs old. He did show favorites with my youngest brother because that was his biological son. Now with my older bros. We had difficult time, a lot of resenting went on in the house But my step dad always showed us love It's not easy. You have to take a step bk and see the real reasons your having problems. I don't see how you can raise your son in the household for 8 yrs and he not love him at all. I can see him not liking him at times. Sometimes I don't like my kids. But there's always love goin on. I see my step daughter every other weekend and I love her and care for her. I have been around her for 8 yrs also. It's hard for the longest time my husband would do everything for her spend ton's of money on her, lack of discipline and virtually let her walk all over him. When I would bring it up he would get mad and brush me off. Latter I found out and understood that he was trying to make up for the loss of time and not seeing every day. It's hard and it sounds like you have given it a lot of thought. I wish you tons of luck.
lots of love