yolo
It's bloody hard and you're human. It's especially hard when you are being physically attacked and have to contain your own adrenaline fuelled self preservation responses.
I'm a big fan of keeping a diary when I need to work something out, strategy wise. I like to dissect events, to work out what the triggers were - often there's more than one. For example, my eldest can be simmering for days, like yours, because there's an event at school that's increasing his anxiety over and above his normal hyper-vigilant levels. It takes something small to trigger the explosion, though - eg having rain blowing in his face, DS2 crying or screaming, not being able to find a remote control.... It's not always possible to do much about the immediate triggers, other than making sure things are put away properly, etc, but sometime it becomes clear that a regular event, or certain days at school put him on edge and make him a lot more snippy.
DS1 has never responded well to positive or negative reinforcement. Star charts bore him very quickly, as he feels pressurised by them and sees not getting a star as a negative event - though, at your DS's age, would equally go out of his way to find out what happens if you don't get a star. All pretty counter-productive. He never cared about having toys removed. If it was gone, it was gone. At any rate, even now, at 10, he doesn't really link a punishment to an event, so things are only confiscated if there is a close link between that thing and the behaviour concerned, eg, he's used a car to gouge furniture (cars go) or is fighting with his brother over lego (lego goes).
Phrasing of requests is something I've found makes a big difference to his response. If I ask him "can we have the table ready for tea, please" 4 times out of 5, he'll put everything away. DH typically tells him "tidy up". 4 times out of 5, he loudly and angrily refuses (changing DH's behaviour, in this respect, seems to be no easier than changing DS1's!) The problem for DS1 with "tidy up" is that, firstly, it's a demand made by somebody else and demands make him panic because he feels out of control. Secondly, it's an activity with no end point. He feels like he could be tidying up forever. Having the table ready for tea is something that he has a stake in, as he wants his tea. The work he needs to do also has a clear end point - a clear table.
A policy I do have, when DS1 is in meltdown, is sticking to as few words as necessary - only use the words necessary to keep him and others safe. They only feed his rage, otherwise, particularly when my own stress is coming through in my voice.
I'm a grizzled, greying 44, btw. Age definitely has nothing to do with it. Plenty of parents younger than you have no difficult behaviours from their children.