Where is your MiL in all this? Does she know &/or care about his drinking? Would she take him in if you asked for her help?
For now, stop doing any 'domestic services' for him. No cooking, laundry, cleaning, admin, etc. And if you have joint accounts, separate the money and put 1/2 in your own name. And do it ASAP before he cleans out the accounts. If possible, move into another room. You want to make things as UNcomfortable for him as possible.
Since you refer to 'MiL' I assume you are married. If so, see a solicitor as soon as possible. You need to educate yourself as to what you can expect in a divorce. If you aren't married but you own your home jointly, see a solicitor.
As far as his drinking, please find your local chapter of AlAnon. It's support for the families of alcoholics. They can help you. And do NOT cover for him and his drinking if you have in the past.
Remember:
You did not cause this.
You cannot control this
You cannot cure this.
He will not stop drinking until HE wants to stop drinking. The only thing you can do is protect yourself and your children by leaving.