Here is my take.

1. He stole $50K from you. He needed you to create an account to create a record of the money going to you and/or because the checks were made out to you, not him.

2. He owes you $50K.

3. Even if that $3K is rightfully his, he still owes you $47K. If that $3K is his (doubtful), consider it a partial repayment of the $50K he stole.

4. Don’t worry about any tax. The tax liability is his as the spouse.

5. Again, anything he says he is owed, if true, is only a partial repayment of what he owes you. Maybe he is owed some money, but make him take action to get it. He won’t because he committed a felony by stealing that money from you.

6. In future, deposit checks into one account and move the money to another one he doesn’t know about.

7. Tell your bank/police that he stole money from your account. Get the image of the deposit check. It will have your name on it as payee. That is all that should matter to police/bank, not whether it is from will vs. insurance. Get the image of the check he used to steal the money and tell the police/bank about the forged signature.

Make sense?

Edit: Get a lawyer. You may need to sue to get that 50k back. Since it appears to be a felony, a lawyer might like the chances of recouping the funds and do it for a percentage of money recovered. This is especially the case of he has assets,like a home, or reliable income.

Edit 2: Don’t pay him to get the stolen money back. He clearly has no intention of doing anything other than stealing more money from you.