Don't like my step son

My step son is 16 and I can't really stand him. My husband hasn't really been in his life. He went to jail when my step son was 2 and didn't really bother keeping in touch when he got out. BUT his mom remarried and he had a dad. He was extremely close with his step dad. To the point that when my step son's mom died when he was 13, my husband just let me stay with his step dad because he wanted to. We only ended up taking him in because his step dad died 6 months ago. His brother got drunk and unalived him in front of my step son. Ive been extremely sensitive of his trauma and have him in therapy but he's just overall irritating. He's extremely unmotivated. We've had several meetings with his school and he failed EVERYTHING this year. I have a rule that we all eat together as a family and he doesn't ever eat at the table. He takes a plate and leaves to eat in his room. He also always comes home smelling like weed. My husband hasn't been putting his foot down at all. The most he's done is put him in therapy. I just really can't stand him and don't know how to get him on track.