@Whatdoesitmatterif
Our eldest has ADHD, and then we have 3yo DTwins, who flit between playing nicely, and playing like Connor McGregor.
Half term when the weather is pants is bloody awful. And this is from someone with a garden, a DH and reasonable budget. You are far from being unreasonable.
The days when it's so cold that we are stuck indoors, I often count the hours to bedtime. Especially if DH is not there, as I physically can not control all three (two of mine like yours, are bolters) when there's just one of me. So indoors we stay, and the combination of being cooped up and no school routine, squabbles are endless.
If you can, separate them. Elder DS will watch a film, while DTwins and I play a game. If they're not together, they're not able to argue.
Make a den. Sofa cushions, duvets, blankets etc. Make two and plonk yourself between them with a cuppa, so they can't poke each other, or knock the other's down.
So what if you spend a lot of time in front of the TV. It's 5 daytimes. The world won't end. You matter too you know, and if this stresses you less, then good. It's not forever. Again, it's just 5 day times.