You are in CA. Child support ends when the child is 18 or graduates from high school, if after age 18 with 19 being the highest age for which support could continue for a child still in high school. In other words if your youngest does not graduate high school by age 19, child support stops at that point regardless.
So, he could be ordered to pay child support for your youngest child, but not the two who are in college.
You do have a long term marriage and he appears to have been the caretaker parent for the past ten years. He likely will be awarded alimony.
Your college age children will not be subject to any custody order. They can live with him, if they choose. They can live with you, if they choose. They can choose to live with neither of you. One could live with him and one could live with you.
However, your youngest child would be subject to a custody order. The court could give custody to you. The court could give custody to him. Children don't get to decide which parent they want to live with. However, if your youngest child is an older teenager, many judges will let the child express a preference. It's up to the judge to decide how much weight to give to the child's preference. Most judges probably would value the opinion of a 17 year old more than that of a 13 year old. But, your child should understand, if the custody issue goes before a judge, the judge is only obligated to listen to child's preference. It will not be binding upon the judge in CA.
You mention that you might retire at age 50. Are you eligible for a pension of some kind? If so, your pension could be divided in your marital property settlement. If you are not eligible for a pension, just exactly how do you propose to support yourself "in retirement"? Your 401k, 403b, 457, etc or IRA also will be subject to division in your marital property settlement.
In other words, don't be a big hurry to retire until you know the "lay of the land".
Divorce in CA is "no-fault". His "mental absuse" won't matter one iota in any decision about alimony, custody or the marital property/debt division.
If he moves out of the country, he might have some logistical difficulties in enforcing the court order that you pay alimony. However, you won't be legallly excused from any obligation to pay solely on the basis of foreign residence.
I suggest that you discuss your situation with a local family law attorney. The question about changing your banking arrangements and the timing of same is one of the question that you should discuss with him or her along with who gets exclusive possession of the marital residence while the divorce is in progress. (Don't assume that it will be you!. You need an order to that effect if he won't voluntarily leave and don't expect him to voluntarily do anything once he is served the legal papers!)
Also, you should assume that he will want his share of any equity that you two have in your home. Can you afford to buy him out?