I've read the book below (quick reader) and I'm still genuinely not convinced he's abusive.
I think he just gets angry a lot. The book explains this is possible. That's not to excuse the behaviour, just that it is separate. Not sure what my next move is, need to go home soon, maybe phone work's counselling service?
Your next move is to admit to yourself that you were scared and moved yourself and DS out of your husband's way when he stormed down the hall. You need to also admit to yourself that you backed out of the kitchen with the cash, and you need to ask yourself why you said in your opening post 'I (stupidly) asked how he'd got it if the cash machine was broken'. Why 'stupidly'? Do you blame yourself for setting him off? Do you sometimes seek to pour oil on troubled waters here, to avoid poking the bear, to control situations in order to avoid rages?
At the moment when you moved your child and yourself out of the way, did you feel that he would have barged right into you or stood there angrily roaring at you if you hadn't moved?
What feeling or sense made you move out of the way?
You also need to analyse these conversations:
DH: are you still not talking to me?
Me: I'm not not talking to you
Why did you say that?
Why were you dancing around the issue?
DH: did you see my texts?
Me: yes (thinks of something sensible to respond with and fails)
DH: (huffily) well I'll just leave you then.
Why dance around the issue?
If you were to say 'Talk is cheap', or 'Too little, too late', what would he say or do?
In this exchange I suggest you were afraid to tell him what was actually on your mind because you were in your own office. Were you afraid he would trash it? Were you seeking to gauge and/or control the level of anger by being neutral?
In his office:
Me: you've got to understand I'm still quite angry, you wouldn't act that way with your friends
DH: yes I would, anyway I don't want to talk about it, you missed your chance
In other words, 'You may be right but I absolutely refuse to talk about it or do anything about it, so shutup.'
Me: that's a bit controlling, you need to recognise it's not ok to behave like that. It's scary,
You finally almost got to the point.
But you didn't use an I statement: 'I felt scared'.
Why use the neutral 'It's scary'?
You used the unassertive phrase 'a bit controlling'. Why?
I sense you are afraid to confront him.
Why?
Now he presses home his advantage:
DH: why, what did you think I would do to you? None of it was directed at you
This tells you he has no intention of admitting his behaviour is a problem. This is your husband shutting you down. He is telling you that his loud and very visible rage and complete physical domination of the space is acceptable and it's going to continue.
Me: errrrrr, can't say I really had time to think about it
You backed down here.
This was a weak response. You responded weakly because you knew you were getting nowhere and perhaps because you are afraid of him.
A much better answer would be, 'I'm sorry you feel that way.'
This tells him he is not off the hook.
It tells him that you know there is a history to his behaviour and that you fully expect more of the same.
It tells him that his attitude is a problem.
Practice saying 'I'm sorry you feel that way'.
Maybe respond to his texts with the phrase.
I assume you left his office, leaving him in his own space. He retained the position of power in the second half of the exchange through his verbal offence, and he disrespected your office in the first half, by negating what you were saying about the effect of his behaviour in your own space. What I see here is that your husband likes to dominate you and has no intention of stopping. Hence the stony silence when you told him he had a problem with anger.
You do realise, by the way, that he doesn't have a problem with anger?
He has a problem with your anger.
He has a huge problem with entitlement. Your optimism that he will reflect on what he has done is misplaced.
I urge you to read the Lundy Bancroft book mentioned upthread from cover to cover. There are 432 pages in the book version. You need to read them all.
What would happen if you were to tell him that his loud and visible rage inside your home is not something private, if you were to state that it is categorically not something he would do at work or among his friends or colleagues, and that he needs to come up with a way to deal with life's little frustrations that doesn't involve scaring the shit out of his wife and son. When he responds with gaslighting or anger, tell him you are sorry he feels that way.
You need to print out this thread and bring it to a counselor.
You need to find a counselor for your son. The damage being done here is immense.
Find someone who specialises in trauma for you both.