Several possibilities:
He's projecting/deflecting (Google these, inc "psychology" "jealousy" in search string) - cheating or planning to himself and so thinks he sees the same behaviour in you. He's judging you based on his own actions/morals. But yes also sometimes so they can justify such actions in their own mind and even later to others, claim it was revenge cheating.
Is there a pattern to when he decides you've "upset" him? You mention sons birthday and that he's likely to spoil this - does he not like others inc his own DC getting more attention than him? Would also explain his not liking you giving attention to another/getting attention. My father is like this. Totally narc & toxic, almost every birthday, Xmas, celebration without him at the centre ruined by overreaction to things that wouldn't normally fuss him. Very jealous/possessive too.
"What is that? Why!" More googling - particularly npd (narcissistic personality disorder), toxic parenting.
outofthefog.website/top-100-trait-blog/2015/11/4/false-accusations-and-distortion-campaigns
outofthefog.website/top-100-trait-blog/2015/11/4/holiday-anniversary-memory-triggers
Think you'll find this site very useful.
"it follows a pattern" another Google - cycle of abuse.
Counselling doesn't change abusers - it just gives them more excuses to abuse.
Plus what theBewilderness said.
Sunshine - counselling where there is abuse - ESPECIALLY emotional abuse - is NOT recommended, nor is staying in an abusive marriage "for the kids" your viewpoint is antiquated!
I left my cheat ex at a point where I wasn't working, was hundreds of miles from family/friends, getting a job was tough etc. Within 4 months I had (with help from the right places) found somewhere else to live, got a new bank account and was receiving benefits, at the end of it got a job and childcare for dd, had started divorce proceedings and was free of his mess! You can do it!
I also think it's distinctly possible that his mother was abused in exactly the same way you are being - less open knowledge then, less easy for women to leave with DC etc. - I think it's entirely possible rather than her 'abandoning' him that his father manipulated things such that she couldn't take her child/ren with her. Have you met his parents?
"His father treated his mother very badly and after several years of similar behaviour - she left him." There's the truth!
Plan your exit. But DON'T tell him or even hint that you're thinking of leaving.
Make sure he can't find what you're writing down, or this thread. Clear your history and log out of mn unless you're safe to be on here. With the suicide threat I too am concerned he could become violent. When safe to do so as well as women's aid contact local police ask to speak to domestic abuse team.
www.womensaid.org.uk/the-survivors-handbook/making-a-safety-plan/#1447926965295-8f67f8a6-62c7
HE IS LYING - you have done nothing wrong. PLEASE get out ASAP!
"because I'm scared of it escalating- it has in the past" what EXACTLY does this mean? Has he physically gone for you?
"slam doors, slam things about" thats still violence and shows that he IS capable of hurting you or the kids.
PLEASE call police/women's aid ASAP
"Also his therapy has now stopped - he only had 8 sessions and his therapist told him that she was going to use him as a car study of great recovery and progress! He definitely did have therapy. With a psychologist not counsellor."
Bullshit! I believe he really was seeing a psychologist BUT NOBODY is cured in 8 sessions, especially with all he's claiming! He can't have it all ways! Either he's cured and therefore nothing you do would be that much of a problem. Or he isn't and he's quit (possibly in temper at psychologist seeing straight through him) or been discharged for not properly engaging.
Does he work? So you'll have a time you can call police/women's aid safely?
Abuse never starts straight away or nobody would stay with them! Did it start when you were pregnant?
Let him go away with his friend - your son will likely have a much better birthday WITHOUT him around and it would give you a chance to get out.
He won't slag you to your joint friends if he has any sense (which I suspect he does) because that says FAR more about him than you!
Where's your brother? I know if I were in your situation and called my bro he'd be here in a few hours, helping me and kids pack and telling dickwad to not even THINK about coming near me!
Actually, he'd probably pack HIS things and kick him out with an "I fucking DARE you to come after her mate, give me an excuse!"
Why didn't you mention bro before? How far away is he?