A lot of readers aren't going to like this but here goes:
There are some jaw dropping accounts here about the behaviour of mothers and mothers in law.
We often hear about 'women with a DH problem', ie when husbands fail to stand up to their mothers.
This may be a man with a DW problem.
Do you side with your mum against him?
Do you just stay quiet instead of speaking up and leave him to be the bad guy?
Does he feel ganged up on? No say in how his children are brought up?
You, your husband and children are a unit. Everyone else is outside the bubble, and having someone encroach in on those boundaries can be very difficult.
If she is an ever present interferer, this never works well.
I think there's a lot more going on here and this is the last straw - it may be that he's had it up to here and is desperate.
My brother finally left when his daughters were grown up after years of interference from MIL and his wife totally sidelining his wishes and needs.
You don't describe him, your marriage etc so no way if knowing if he's worth keeping. Is he a good husband, father, lover? Is he kind, respectful, your soulmate, your friend? Basically - do you want him back? If yes, he's told you he can't do this any more, so 'this' has to change.
Whether he's come home or not, you need urgent talks. Calm, controlled adult conversation. You need a united front, shoulder to shoulder, agreeing your policy and attitude to your mum. And stick to it.