Please give me some advice

Back story - my husband has full sole custody of his 9yo son. His bio mother hasn’t seen him since he was 2, and has made no effort to see or talk to him. She kind of just left him with us on our week and never would make plans to get him for hers and eventually just stopped all communication. She didn’t even show up to the custody hearing.

Dss and I had always had a good relationship, we took right up with each other and got along great. I potty trained him, taught him to write, count, his abc’s, etc.

then he started pre-k, teachers were noticing his lack of concentration, very hyper, etc. we had noticed this at home and figured he was being a typical 3-4 year old and it was just his personality. Kindergarten comes along, teacher says the same but has now added that he is very defiant. I look it up and notice we are seeing the same at home. So we really started reevaluating our discipline and how we’re reacting to things(we had the mindset, he was lacking a parent and were disciplining with sympathy bc of that.), so we started taking toys away and time out. But, instead of redirecting him, this seemed to be making it worse and he started with the anger outburst. In 2nd grade he was diagnosed with ADHD. He is currently in 4th and when I tell you that every year has been absolute hell, that’s exactly what I mean. They just finished the first nine weeks and I received a 45 minute phone call from his teacher. He is being defiant, telling them no sternly, disrupting the whole class to the point that “she had to just stop and embarrass him in hopes that he would stop”, doing everything he can to get attention, not doing his work, etc. he has seen a counselor in the past for a year and a half exactly and seen no change, he was being studied for ODD(oppositional defiance disorder) and we switched therapist before that diagnoses was made definitely. The therapist we switched to closed practice shortly after and we have not found a new one. It has gotten to the point that he will hit me, threatens me when I discipline him and even lies about me hurting him. Just recently at my 9 month old sons check up, dss smacked me(in front of the doctors), I did not react because I honestly didn’t know how to. As we were walking out he started crying hysterically saying that I smacked him, in front of a whole waiting room. My mouth fell to the floor and told him to tell the truth(and he kept on with his story). Thankfully the doctor saw what played out, otherwise he could have really gotten me in trouble.

I’m just at my wits ends. We ground, we take things away, he writes sentences, he has extra chores, he even gets rewarded for his negative behavior at times by going to the movies or ice cream nights just bc we feel like maybe he feels he’s not getting any attention(though he does). I don’t want my own child to be in a separate home from his father, and I don’t want him growing up with 2 stressed out parents, and I don’t want him growing up learning these behaviors. But I’m at the point that I cannot be around my step son anymore. I don’t want to be in the same house with him. I don’t want him to feel like my husband chose me over him, but he’s over it too. We literally are out of options.