@TakeTheCuntOutOfScunthorpe
I think the point the OP is making is not that they share a hobby and she feels excluded - it's the sheer amount of time they spend on it, and the lack of support from her husband when she tries to set boundaries.
I don't have anything against games, I used to play when I was still at my parent's and my brothers had consoles. But in my late teens I just went off it. Think it was when they started making you do all the boring stuff of life in a game, like getting food and refuelling a car!
But I do think it should have time limits. OP you also said your eldest went from "YouTube to PlayStation to phone" - I know it's not the 90's anymore but why does a primary age child have a phone?
I'd suggest your husband that gaming time is between so and so time and so and so time, and if he wants to do more on his own he can fit it in between shopping, cleaning, laundry, cooking, bathing, etc., etc. If he wants bonding time he needs to all the admin too.
There must have been a time when you first met that he wasn't gaming where you fell for him - people can change, sometimes not for the best, but is it worth reminding him what you saw in him to have two children with him, and that that is now missing?
Take time for self-care, forget about all the life admin for a while and just do what you enjoy. It's better to have a messy house for a while than burn yourself out. Only do things for yourself, obviously don't neglect your children but rather than force things on them, when they come looking for food or whatever, show them the whole process and explain how much time you spend on doing things you don't necessarily enjoy doing.
If they want something else to eat, take them shopping for it, give them the list and they can find it themselves.
Definitely don't do anything for your husband. If he's an adult he can look after himself. And make it clear that you're close to leaving.
Then, if you have somewhere to go, just go. And to be honest, with or without your children. He's a parent too, he should be able to cope, and if he can't, I don't think custody will be a problem.