I'm at the end of my tether, and I need advice please. I have just split with my partner because of his BS aged 15.Who I will refer to SS from hereon

Lots of things have happened but I can only start at the beginning. I have two BD aged 17 and 11. I met BH 2 years ago he was not speaking to my SS (then 13) because his son would have nothing to do with him after the split with BM and also BS had DH reported to Child Services for hitting him on the arm (which came to nothing) He wished his dad dead and was rude everytime he saw his dad. My BH has another son aged (9) at the time with whom he had regular contact and a great relationship.
I didnt agree that my BH would buy BS (9) presents and not the other son, my thinking was he maybe angry but he still needs to be treated the same as his brother, and even if only to try and mend the relationship.
After 6mths of being together I managed to get SS(now 15) to come to his dad's birthday meal asw I was meeting ALL the family for the first time, we got on like a house on fire. After that BH moved in with me at my rented house and SS (15) came to visit each weekend and some days throughout the week. HE was a very opinionated child, swore a lot and didnt really respect adults in general but BH and BM allowed this to happen, which cause a bit of friction with my BD but it was soon sorted out.
After only 3 weeks of living together BM of SS (15) phoned to tell us to pick him up as he was being abusive to her and her new partner, I went and picked him up and talked to him, he said that he would never accept his BM new partner andd that he hated him. We sat down and discussed it together as a family and told him that he had to make a bit more of an effort with the paretner as that was who BM was hapy with, two days later he went back home to BM. LEss than a day after another phonecall he'd gone and hit his mother, apparently his mother had hit him first blah blah blah. I went again to pick him up and told him that he should stay with us for a week to cool off.
BM turned up two days after with his suitcases and said she'd had enough of him and that he was now our responsibility... I happily took on the challenge. He refused to speak to his BM and refused to see her if her new partner was around.
BM moved away with her partner and the other son a week later (I think she'd had it planned from the start)
Bearing in mind that BH and I had only been living together for a couple of weeks and that BH has only had contact with his son for no more than 2 months I took SS into my home.

After 5 months things started to go very wrong, he was verbally abuseive to me, swore at me, called me names etc, he refused to eat at the table with us, and stole food out of the cupboard to eat in his room. So we went to a counsellor who told us that it was difficult with blended families. My youngest BD was having a few of her own issues with BH but I had the full support of my ex husband in the way we were dealing with things.
Enough was enough at christmas we'd bought him the item he'd wanted and told him that he would have to give $100 back to us as the item was $100 more than we'd spent on the other 3 kids, he completely blew up at me called me all the nbames under the sun, told me how he hated living with us and so on. So the only alternitive we had as his BM still refused to have him as he caused her too many problems was to send him to BH parents for a few weeks, that lasted 3 months before he said he wanted to come back. The counsellor told us that we had to establish rules together as a family so we sat down and talked about the rules and put them up on the fridge for all to see.
SS constantly broke them, he tore them off the fridge, he smashed things (this was MY rented house here!)We did as the counsellor said, ignored bad bahaviour and rewarded good.

We eventually moved into OUR rented house a big one as there were 6 of us at the time, but 2 weeks after moving in me and my BH had a huge fight. SS moved out to grandparents after verbally and almost physically assaulting me and hasnt spoke to me in nearly a year, he now refuses to accept me being with his father.
He has a great way of making dad feel guilty and manipulates him. To the point where in June BH moved out to be with SS. Tehy now live on their own, we continued our relationship until 4 days ago as I couldnt stand not being with BH on a full time basis any longer.
I am not allowed to the house because of SS, I cant attend family events because SS is there, and BH can only stay over 3 nights a week.
I am now at a point where I think I may have made a mistake regarding my relationship. BH and I get on really really well, are in love, happy and my two BD love him to pieces, I have given BH a month to sort some thinhgs out as this cannot continue, ss is holding him to ransom, BM wont have him.... how do I cope with this.... or do I stay away because it will never improve and SS will never accept me????

I need a little or a lot of advice please I'm desperate. Thank you