How can I stop my husband from spending his 401k on his 50 year old son.

How can I stop my husband 26 years from spending any money from his 401K? Or get it divided in half. My husband has a 50 year old criminal son that lives in FL and he has been supporting him for years. My husband believes anything this kid says even when other people tell him it is not true. My husband has spent over 100,000 + more. And is getting ready to cash in his 401k soon if he has not already. Or if I can collect half of this money and put in my own bank account, or even make him cash it and put into an account we both have to account for any withdrawals. I am seriously worried about what will happen to me if something happens to my husband. I have no family. I need a guaranteed small nest egg. I have no access to the accounts he has been taking this money from. He also spent 62,000 from our regular bank savings. That was his last check when he retired. In Dec, 2016. He had a huge inheritance back in 2009 or 10, and he kept it from me. I realized it was his money.