@pinkypie22 Him bring in a comedown is it an excuse either.
Please don’t be afraid. Report it to the police once you have already got exit plan in place or you are on your way to safe space. Or be very clever and make him think he’s won by saying “I think you’re right, I’m no good for you and we should be apart and raise our son just as friends, that will be best for everyone” and say you’ve already sorted a place you can stay and off you go. Say you’re sorry it didn’t work & sorry you caused so much trouble for him & goodbye.
Then as soon as he’s deflated and diffused from this (he won’t expect it and it will bring down his attack reflex because there’ll be nothing left to battle for...and he’ll think “oh...?” And be confused so he won’t do anything... THEN you are away and you can call police, report the assaults in past with grabbing and stuff, verbal assault - how often and what time frames, say why you left with your baby and that you we’re afraid of his reaction because he uses drugs and frightens you, calls you names, you get in trouble if you don’t follow his instructions etc. Then he will have hardly any chance of getting shared custody of your son if he tries to use your son and a custody battle as a weapon to punish you for the embarrassment that he feels and rage he feels at losing control of you and you actually leaving. If he thinks he’ll have to take drugs test and have his past delved into by police he won’t want to take you to court.
He is lacking empathy yes and possibly has a personality disorder such as narcissism .. these types of people often don’t have developed frontal lobe function meaning poor impulse control and rage and this is made worse by drugs, but even without drugs, it’s just how they are from childhood and won’t change without extensive therapy or prolonged sobriety. Even my ex he is sober now and he is the same except just a bit less volatile or extreme. He still does the mental torture and games and he still loses his temper with my daughter and is a compulsive liar and master manipulator. This is all without drugs and he apparently now meditates all the time and turns up with meditation beads around his neck. It’s all show to make himself look good to the world and to his new gf. His behaviour and attitude /bullying nature is the same. HeMs like a Ted Bundy style manipulator character who makes everything about HIM being the victim, to deflect from anyone looking st the awful things he’s done. It’s textbook.
You cannot make anyone want to get help, they say they will in order to continue controlling you & keep you where they want you. They threaten to leave but that’s another control tactic, they don’t want to leave because that would mean saying goodbye to the source of what makes them feel powerful and strong - making you weak and small. And it would threaten to expose their behaviour which they are lying to themselves about and don’t want to take responsibility for. They can turn very spiteful and vengeful if they think you’ll expose them and you are no longer under their control.
Look up narcissistic abuse and see if it sounds like how he is to you...?
The hardest thing is to admit to yourself is that it’s not drugs, not personality disorder, not undiagnosed this or that, none of those things ever makes someone systematically abusive for that reason alone - it’s a rational choice.
If he was mentally ill or in a drug fuelled frenzy he would not have been able to control himself at all/ he wouldn’t be able to confine it to the house/ just to you .. he’d be out there on the streets not caring what anyone thought of him, just acting out, screaming at you in public, dragging you along, yodelling, beating his chest, punching a car parking attendant, Smashing someone’s wing mirror off....
He can control it and he can choose when and how to do it. Behind closed doors, subtly at first, designed to control you and frighten you into doing what he wants. It’s calculated & deliberate. Everything else is at fault but him.
Don’t let him scare you into inaction by him saying - LYING - that “you’re crazy, the baby should live with me” etc... It’s all a scare tactic to make you scared of “what he will do, if I tell someone”.
He’s probably got a record .. maybe he’s done stuff like this before to other women.. or his daughter. But he’s set up an environment in your home/relationship where you’re afraid to even check any of these things & you’re too confused and caught up in his world and his excuses for his behaviour and him blaming it on you that you can’t think straight.
So he protects himself by making you so confused and tired and stressed that you can’t think straight to see him clearly and do what any “normal” person would do (and by that I mean someone who’s not been slowly conditioned by him) and - RUN / report him.
If a random man came in off the street into your house and treated you like this, would you call the police ?
He knows he’s doing bad things to you & treating you like a disobedient dog. He knows this is not how you treat your gf or mother of your child. And he also knows some pretty powerful ways to avoid getting found out. By brainwashing and scaring you at your weakest and most vulnerable moment - as a new mother. The sort of person who will do this, is not someone who needs help and understanding, not st this moment in time. Maybe way way down the line once you’re away and un-brainwashed and you want to create an amicable co-parenting relationship for your son. But with this kind of person it’s often not possible and it’s more damaging to your mental health and to your son to try.
If you could come out of the fog and see it for what it is and snap out of his spell - you would be able to think clearly and do the sensible / safe thing which is to enlist help of police to get far away and protected from this man. Don’t lose years of your life and your sons life hoping he’ll change. And seriously damage your own mental health in the process. The biggest mistake I made (one of them! 
was being SO wrapped up in what HE was doing .. that I was not present for my baby daughter. I was not. I was obsessed and on edge about HIM. I will never get those newborn times : that first year back. She got a preoccupied, traumatised, emotionally unavailable Mum for her early life and she was traumatised from this, I know it. I found it hard to bond with her and develop proper mother’s instincts to protect her because I was more brainwashed to be pre-occupied with him and trying to keep him sweet or trying to fix him. Even when he used to drop her in my lap when he was too impatient for me to get my boob out to breastfeed her or he would grab her roughly because he was annoyed with me... I still kept telling myself “he just needs help, if only this or that.. he’s just scared of being a Dad or tired.. or if only I could get him to stop taking drugs...” I was brain washed ! Desensitised to this abnormal and abusive person. Thinking I could fix him or help him. Using all my energy on that. So I became his enabler. To stay the same, as he knew I’d always make an excuse for him. And he knew I wouldn’t tell anyone. So it gradually got worse. Until he threw me across the room & hit our daughter. She still is massively startled at loud noises & has night terrors because of all the shouting and crying she constantly heard since she was in my belly. It messes them up, don’t think because he’s a baby that he won’t get effects from this.
If this man is going to change it’ll be when he’s lost everything and been sober a LONG time not 3 weeks. He’s confident you won’t leave and he’s confident you’ll keep taking this treatment and putting up with excuses so he’s also happy to lie and tell you what you want to hear in order for you to keep doing what he wants and keep you where he wants you and where he can influence you.
Steps to heal:
Women’s Aid - Freedom Programme
Read : Codependent No More
& Why Does He Do That by Lundy Bancroft
Go No Contact with him or as minimal contact as possible.
Run far away & get many professional people in between him and you so that he cannot suck you back in by feeling sorry for him, feeling guilty that you’re “splitting the family up “ — you will have all these feelings and they’re normal but they are not real.
The only reality here is that he is abusive and this relationship and being around him is damaging you and your son right now possibly long term.
Maybe in future he will get a bit better or make some life changes for your son, but st 40 it is doubtful. And it is not your job to fix him or make him see. The more you try, the less he will.
Also take responsibility for making this choice to be with this person and stay with him, and forgive yourself for it. But don’t keep making the same mistake. Xxxxxx