Good you have found your angry.
It is so very hard to excepted someone you trusted more than anyone can walk away from you and the children. This is not someone you want in your life.
Legal advice will be a good start.
Arrange to get 3 valuations. It is good information to have.
Claim benefits. UC take up to 5 weeks to kick in so don't delay and put in a claim to CMS. go through them as further down the line you don't want to be arguing with him over money. Let them deal with it.
Council tax benefit you will get 25% reduction as a single adult. Go through your direct debits. Hand back all his bills car. Phone etc. And look at anything you can reduce or cancel.
Contact is agreed at a set time and day. Every Sunday and Wednesday tea time. Whatever works for you. The children then know where they stand.
Get support for you. See your gp. Look for local counselling services. This will help get your thoughts in order. And give you a safe place to rant
Start a diary if you are concerned about his ability to parent safely. Keep notes and you can use this for reference. Notify school/childcare setting so they can support your children.
Go as low contact as you can. This one is hard. But it is time to draw a line. Contact is about pick/up drop off only. Money is via CMS. And house via solicitor. Show him you are taking control and mean business.
I know the house feels important right now. But long term that mortgage is going to hold you back. And do you really need such a big house? My priority was to be able to enjoy my children whilst they were young. So cutting my out going was a priority to maximise my income.
It doesn't have to be now but maybe 6/12 months time you feel more prepared for a move it will be a fresh start for you and the children. And to be honest I think you will struggle with the mortgage. Mine is half that. And I earn the same as you. And I am struggling to find a mortgage that will excepted benefits/CMS. For a £100k mortgage.
It is going to be a roller coast of emotions. But you need to show him you won't get pushed around. Feel free to pm me if you want a understanding ear. I'm 2 years down the line. (Younger more fun OW here too and the drinking) You will get through this. Because there aren't any other options. You will come out the other side. Stay strong. You deserve much better than this excuse of a man.