I think what you're describing is PTSD in an aware person that is going through treatment.
My SO is...
Eh, sorry but no one's stress response is too f*cked up to do that. I've been there too when my PTSD has been unmanaged. Mine was delayed onset so i had no idea what was happening to me when it kicked in - I thought I was going crazy, I was terrified. I had the rage, I had the terror, I had the high-stress waking nightmare and still have some of these to various degrees - my 'stress response', pain, panic, fear, rage was through the roof but I never abused my boyfriend. I'd never abuse anyone. Why? Because I have empathy and I have a level of behaviour for myself, I would never abuse anyone no matter how I feel.
Yes, he 'can't' stop himself from belittling and insulting you because that's his level of morality, that's what he thinks is acceptable. See if it is about control - how come he does choose to stop at strangling you (at the moment)?
Anyone that says they have no control over being cruel to you is talking utter shit. It's always a choice and it always fits into what they think it acceptable. Look at this way, if someone were a cheater - and they put it down to them not being able to control their 'urges', if you looked at that situation carefully then you'd see that it's not JUST about the 'urges' they have - someone has the urge but they also have the moral framework that leads them to think that that kind of behaviour is okay.
Why do you think he's not capable of the choice not to harm people he loves? Why isn't he? Shouldn't he be held to that standard? Aren't you worth that? I say that with compassion, not judgement. Also, if his stress response is out of control then does he have equal issues with abusing everyone he meets? Stranger or not? Or just you or people close to him? Surely if it were an 'out of control thing' then he'd be abusing everyone.
This is abuse, it' wrong and it's a choice.
This article contains quotes that are also relevant.
Lundy Bancroft,
Why Does He Do That?: Inside the Minds of Angry and Controlling Men
I'm going to drop it, but you can be certain that none of this crap is PTSD. If it were then everyone with a TBI and PTSD would be doing it and we aren't. Managed or unmanaged (as my PTSD has been).