To split up with DH because of the children

[CompletelyNewAgain]

Both DC severely autistic and other disabilities. They scream and attack us all the time they are awake and between them that is around 20 hours a day.

We do get some short breaks and asked for social care respite last year. The respite worked for a bit but literally in the end it was more stress than it was worth and we asked for it to stop. Family are unable to help us anymore due to the extreme nature of their needs.

I just keep fantasising about splitting with my DH (who I love dearly and does childcare 50:50) so that we can have separate houses, share custody and complete breaks from the DC. I actually couldn't cope anymore so went upstairs and abandoned DH but the screaming is just continuing and it's raising my heart rate. I am in fight or flight mode constantly. I feel such a failure and deeply regret having children.

I want to send sympathy and some kind of encouragement which means might well sound a bit lame. I can slightly imagine your situation because I have a tough time with a child who's probably only half as hard work or less (ND).
My reaction to your original question was that it didn't sound at all crazy to consider separating from your DH, keeping separate households and living the best family life you can figure out. Not your fault there isn't better support.
I have occasionally resorted to ear defender headphones (playing Classic FM or Mindful meditations) it just reduced the problem a bit.
I'm really sorry and sad you're having such a horrendous time. 🏆 xxx