Start stashing cash since California is a community property state. It sounds like he may turn vindictive if he finds out you have another account with money to bail. I did this when I thought me and my wife wouldnt make it. It's been 12 years but I think the key was keeping all of our finances separate. She has her share of bills, I have mine. We agreed not to to touch each other's finances if it ever went south. We argue about almost nothing now.
That's fair.
Sorry for spelling issues ahead of time, I'm on mobile.
I went through an extremely turbulent relationship before my wife and I got married. I wasn't doing great financially and she was basically carrying me alone. We didn't even live together! I barely made ends meet, was a deadbeat for a while and didn't do much to meet in the middle.
My girlfriend hated it. She loathed me, and did not respect me for it. To this day she still has financial woes and reserves about how she carries me for years and now is the major earner in our house (especially since I got a lateral move at work which came with a pay cut and then Covid hit, and now I am taking unemployment waiting to go back to work. I'm immunocompromised. But that's a different issue.)
The facts are my wife found a counselor. At first it was for her, to help her get through this. She needed emotional stability. Turns out it was a good counselor, because some of the things she said when we talked about her experience were really positive and eye-opening. Later, I was invited.
Note that our counselor actually suggested she break up with me because said she saw a selfish man who wouldn't change. I didn't know this, but after going to counseling and really listening, talking and hearing my girlfriend talk, I realized that she was something that I wanted to stay in my life.
I made it work. It took three years of counseling. After that we got married. And we still had some struggles. I continued to have problems with money. It wasn't a total regression, but it was a lot of hard work. Through it all I realized I had made errors and needed to be responsible. I pulled myself up and started taking extra shifts and together, we paid off $40,000 in debt I racked up because I was a selfish idiot. (that was new debt I racked up after we got married, too. she was pissed.)
Now we own a house, I exercise responsible communication with my wife (we talk to each other and budget in things we want) and we discuss what needs to be sacrificed to move things up or down. We have saved up an emergency fund in case we lose our jobs and now have six months of bills and food in the bank and are starting to invest in our retirement again. All through this, we have loved each other and know that each day is another day to show that. Some days I'm not feeling all about my wife, but it's the underlying furnance which keeps my life burning. And now I have a great career job and we're planning vacations and more 
I'm 37. I met her when I was 26. We got married 6 years ago.
Look, I'm not trying to come down on you for wanting to divorce. Money matters are hard. I'm down on the notion that, without fighting as hard as I did and learning to sacrifice, compromise and most importantly put my wife first, I'd be in a much different situation than I am now. Both my brother and brother-in-law have had their lives shattered by young divorces, one was infidelity and the other was, well we're not sure but we think she used him to get through college. She was a brick wall when the family got involved. She refused to go to counseling and it hurt all of us.
Money is so... meh. It comes an it goes. I think some of the advice in the thread is great. My sticking points I mentioned were of the herd mentality to break it off and run away, which I thought was insensitive. If you've already made your mind up, alright. I'm just praying there's a chance he'll wake up one day before papers are on the table and realize he can fix start acting like a loving, caring husband and meet your needs of money matters.
Again, rooting for you guys to make it through this. And if you don't, I don't have anything else to say about it other than I am grieving for you both.
I understand the need and want to protect yourself. I feel , personally, once you start that move it's a drift towards separation as it's about you and not "us". I would really try to get family/friends involved in suggesting counseling to him. If that doesn't work then you're really pushed towards the options of separation. I'm sorry for the toll this takes, been there done that.
You can't make people change, they have to change on their own and want to change.
