[Solved] Strange behaviour

OK, so I haven't posted here for some time and unsure wether to post here or in Legal. Son who is 7 now hasn't seen bio mother since January after Childrens services suggested stopping contact. This was only meant to be a short term thing until we had established some sort of way to reestablish contact with minimal safety. Anyway, things haven't quite happened that way as I will go in to later.
On to the behaviour. Since around a year ago son's behaviour had started changing. Becoming very disrespectful to both myself and step mum (whom he absolutely adores). Moreso the other children in the home of which there are 2.
He developed a tic (a bit like tourettes but with body jerks too), this initiated a doctors visit, referral to local hospital, 2 x A&E visits because it was constant, got to the point son was being hand fed on my lap by my wife because he just couldn't stop 'jerking'. Fast forward to March this year and his teacher advises us that she doesn't think it rings true. something is not quite right and without wanting to dis credit son we believed him further when he told us he can't control it. We then received a further referral to a childrens hospital with regards to the tic and his behaviour. It was only then, 9 months on after developing it he admitted lying about the whole thing and that was ONLY when the paediatrician wanted to do a blood test. So there we sat feeling completely stupid for believing him when no one else did. He had lied.. about the whole thing.
Since then his behaviour has worsened, he steals, lies so much I actually have trouble believing him. On one incident, he was so convincing I even believed him over my wife who was stood there with the evidence in her hand. This obviously created tensions with my wife.
He is not remorseful for lying, he seems to have no feelings whatsoever for anyone that he hurts.
He takes all of his anger out on his step sister who is 6, she very kindly just wants to hug him afterwards when he says sorry but quickly reverts to being mean, a bully and really unkind.
It all came to a head this weekend when he grabbed a piece of Lego and pushed it in between the toes of his sister which judging by the mark, really hurt. We have now made the decision to separate them. Whilst my son remains in his bedroom because I nor my wife can supervise all the time the other children are downstairs. I have given him toys and books so that he isn't bored but this is no way to continue.
I admit to clipping him round the ear 2 weeks ago when my wife was telling me what had happened while I was away (I work away sometimes). My son was just stood there smirking, finding the whole thing funny. For us this is crisis point. My wife is having counselling because she is feeling so anxious and vulnerable and her counsellor made a referral to Children's services who have suggested doing an EHA. The school are involved and are helping albeit gradually.
My son received help from healthy minds who just told us he needs to be loved but seriously it is tearing this family apart. He has started self harming and talks about being suicidal but I dont feel that he is being genuine on that matter.
The problem is my son says the right things to the right people and then reverts when they are gone so to his teachers is saying Im sorry for doing this and sorry for doing that but then comes home and does it again. Dont get me wrong, I dont expect to build Rome in a day but his behaviours are very much in line with that of his mothers who has EUPD.

On to the contact side, obviously we followed the advice of CS in January and ceased contact. We nor the mother have returned to court. We have had no contact from the mother asking how son is, intact the only contact we have had is abuse. In relation to this she has been warned by Police to stop or be arrested for harassment.
Going forward from January and discovering the extent of trauma son has been under was a reason enough to not pursue further contact and at this moment in time I do not believe that reestablishing contact with mother would be beneficial to my son.
I am torn with my wife because she feels that mother should be alerted to the situation and circumstances of that and should write a letter informing that this is what is going on, at present we dont feel contact would be beneficial but she is more than welcome to pursue contact by going through the courts.
We need major help and my wife is fighting tooth and nail for it. 3 years my son has lived with us and not once have we been offered any thing at all.

Please help by giving any suggestions, we are currently waiting on our third referral to CAHMS.