I know, it is so crazy that he is doing this. But as hard as it is to believe, he *is* and you just need to take it from there. One day, one step at a time. You have already shown yourself to be incredibly strong. You can do this.
Some additional advice I gleaned from the boards that might help:
-- set up consultations with the top three D lawyers in your town. Once they've consulted with you (normally a free hour on the phone or something) they can't represent your H due to conflict of interest, so you'll have your pick of the top Ls and he won't have access to any of them.
-- with him starting to clean out accounts, you need to immediately (if you haven't already) set up your own accounts where he does not have access and be sure your paychecks, etc. go there. I'd cancel joint credit card accounts. Some folks recommend moving half of your assets to an account he can't get into. I don't know about all of this but you should at least speak to an L and look into what is best for you right now, given his behavior.
-- in my state, if your H runs away and spends $$ on his "special friend" (as one of the Ls I spoke to called it) the judge will usually put those expenses exclusively on him. Debts run up in the same way can go to his side of the ledger. Document it all. Do you have a good handle on your entire financial situation? If you don't, that might be a decent way to spend the weekend while you wait for an appointment with an L.
I know you wanted to be able to provide stability for your stepson with all of this plus COVID and his senior year. Hopefully there are still ways you can communicate to him that you're always going to be there for him, will always be his family, he'll always have a home with you, etc. even as you go through this. (you might ask WF's advice specifically about this as she was really concerned about her teenage stepdaughter through her whole sitch too).
I'm so, so sorry this is happening. Stay strong.
Me (46) H (42) M:14 T:18, D9 & D11 4/19 - 12/19: series of escalating BDs 9/20 - present: R and piecing