I can’t put him in his own room or remove him as of course he won’t stay there as he’s out of control himself. There’s no where I can lock him in! Removing myself means he’s not getting attention in those moments until he calms down which seems to be working.
If you have found a way to do this which is working then that is good. Sometimes if I really can't get space because one of my DC is following me, I have locked myself in the bathroom, or sat on the other side of a door so that it can't be opened.
I’d lke my son to be able to feel the anger but learn to deal with it better- something I never was taught to do.
In general, the best way to do this is outside of the moment. You can't do any kind of teaching of anger management when they're already angry. However you can do a lot of talking about emotions, thinking about strategies to use, practising strategies etc at calmer moments and then the more familiar he is with them, the more likely he is to be able to use them when he is feeling angry.
I’ve also enacted some pretty big consequences to try and break the habit like “if you hit me between now and tomorrow we won’t go to X’s birthday party tomorrow” etc .
Again if this is working, then I do not mean to stop, because I am a full believer in different things work for different families.
However, IME sometimes the problem with big consequences is that you can end up threatening something you really don't want to have to follow through and that can be hard to manage as you find yourself looking for loopholes, which undermines the authority you're trying to create with the threat. Or another possibility is that you threaten something in relation to a condition which is actually really hard for the child to meet. I mean, hopefully "no hitting me for 1 day" isn't too hard to meet, and indeed, sometimes you can find out from something like this that what you assumed was too hard for them is actually something they can control, if you actually respond to it consistently enough. But depending on the child's other skills (e.g. communication) they are able to access while frustrated, their impulse control, and their ability to retain non-immediate consequences in mind in order to alter their behaviour in the present, sometimes it's legitimately too big of an expectation and they will not be able to manage. When this is the case, the big consequences quickly become counterproductive as they are not working anyway, the child feels it is unfair/impossible and you end up punishing them all the time or even running out of things to take away, or removing things for so long that the child doesn't even register it as a punishment any more.
If you're getting stuck in that cycle, there are two things you can do to alleviate it.
One is to break the behaviour expectation down into smaller parts, which might mean a smaller time period (like schools often use behaviour charts which track behaviour per lesson rather than having the expectation that the child behave perfectly all day before they receive a reward for this effort) or might mean steps between the current behaviour and the expected behaviour. And if it's still not helping, then break it down further.
The other thing is to have a consequence which is really small and generic and temporary, so that it feels less like a weapon and more like a penalty, and so that it has an effect whether you have to use it 1x or several and it doesn't ever run out. Or you can flip with a tiny incremental reward which is either gained when they do the thing over a short period of time or assumed to be given each day but can be lost for any incidence of a behaviour.
And what is important with both of these things IME is to keep the behaviour expectation/consequence structure clear and consistent, so it doesn't feel like he's fighting against you but he's working within a clear system, and then you can be on his side. Like you don't want him to lose his 1p or his screen time any more than he wants to lose it, so you can work with him to remind him of his methods to manage anger for example.
One of the benefits of the consequence being temporary and/or the period of time being short is that it means they always have a chance to try again, which is important otherwise they get discouraged from trying to change their behaviour.