Take a deep breath.
You are doing a remarkable job of bringing up 4 kids on your own with NO help or financial contribution from their feckless 'father' Give yourself the credit you deserve. 🌷
With your 'partner' what kind of decisions did he influence? Did he influence you changing jobs?
Why do you regret changing jobs
It sounds like you had had a dreadful childhood. I presume your sister shared that childhood? She seems to have learned that prioritising the 'man' in the house is all that matters and the the mothers role is simply to prop the men up. You need to shut her opinion out - she needs help too, but right now that can't be your concern.
You went from a dreadful childhood to a dreadful marriage and are now living in a terrible situation where your growing sons are starting to treat you like your father & their father and you're allowing it because you don't really know any better
Your eldest learnt from his father how to manipulate you & sadly due to threatening to commit suicide has made you even more fearful of telling him how things are going to be. This has to stop, both for your sake and his. You owe it to yourself and your children to be the parent in charge.
Definitely do NOT have a house/family meeting or give the children any say in how the bedrooms should be arranged. They already feel their opinions matter more than yours! NO NO NO you need to take control NOW befire it's too late
Your 7 yo us learning fast too, get that nipped in the bud.
Tell DS that the x box stays in his room as does any other anti social behaviour
The sitting room is for all the family, not a space to be monopolised by the boys.
If I had the money I'd get a builder (with some experience) in your see what can be done upstairs, often the walls can be completely move to redesign the space entirely.
It's SO hard not being able to see it or not knowing how big the rooms are, but I wonder if you could rearrange it to get a double room for yourself, a box room for one DS, shred room for DD's & one down in the extension I think you should have a double room (and I'd prefer one upstairs near the bathroom (assuming it's upstairs))