Oh OP this is hard. I agree with PP on the violence, but I do wonder if there are other things you can do to make your life a little easier on things like the wilful pyjama behaviour.
Eg there is no universe in which I'd have had that fight, I couldn't be doing with it. It's very easy to give advice and of course you know your own child best, so take what's useful and disregard the rest but broadly:
I use the tools from How To Talk So Little Kids Will Listen. Make it a game, make it playful. The old fashioned ones work best in our house. I bet you can't get your jammies on by the time it takes me to go downstairs and get a glass of water. If that doesn't work, I explain: boys who don't wear pyjamas will get uncomfortable at night. When I feel like there's going to be an escalation, I won't instruct or ask, because it just gives them the tools for defiance. Making it their idea is a great thing.
But of course I don't always have the energy or emotional wherewithal for that, and sometimes it doesn't work, so I've just started being a bit FAFO about it, and just state natural consequences really clearly. If you don't wear pyjamas, it's likely you won't be able to sleep/will wake up uncomfortable, and just to be clear, if that happens in the middle of the night, I will not get up to help you.
Sometimes very calmly stating the natural consequence, not the manufactured one, seems to work. Sometimes it doesn't, so I stick to my guns.
But it's hard, and laid out like this makes it sound so easy and that's not real life. But as others have said, you have a duty to keep your other child safe so you are going to need to tackle it somehow