What is it you want to know about doing next?
You say you have the important things so I'm guessing that included documents and certificates?
Do you have a joint account with him? If so I would say your next most important thing to do tomorrow would be to open a new personal account - I would strongly recommend with a different bank for all sorts of reasons - and contact anyone who pays you any income (employer, dwp, Hmrc for child benefit...) to ensure they change ASAP to paying into the new account.
Are you working? If so I would recommend informing them of the situation so that he cannot obtain info from them re new address etc Put anyone else he's likely to try and track you down through on notice too.
Ditto any childcare/schools, plus it's good if they know so they can support the children.
Have you injuries from the assault? If so get that documented ASAP, check in with your dr so there's an official record, even if you decide not to pursue matters at this time, this will at least give you the option to do so in the future.
If you're working but on a low income get any benefits claims in ASAP as it takes a long time for them to be processed and even longer at the moment due to covid.
I can't think of anything else right now, I hope the above is useful to you.
As pp say you are INCREDIBLY brave and strong for getting you and dc out of this situation.
Don't be tempted to return, not only because you don't want to be dragged back into being involved with him but because he will likely feel he has little to lose by assaulting you again at this point. Please please stay safe
Good luck 