Executor of the estate car title question?

My mom was killed and her husband and her were seperated at the time. He signed over all rights to her and the estate when she died to me (being that he didn't want anything to do with her or her bills). The Toyota Tundra and it was only a year old when she passed. The credit union at her work financed the truck loan. It was in her name only I have the loan docs. The insurance on the loan paid it off and somehow her husbands name is now on the title with her name. He wants the truck now and has claimed he has reported it stolen.
What can I do? I have all her bills some of which I paid off not knowing at the time I shouldn't have. Can I really get arrested for driving a stolen car? I don't drive it much but I don't want my children and I to be in the car and go to jail for a stolen car
My lawyer says I should not put any more stress on my self and just give it to him. "Just for get about it" she says
I live in California What do you think?
I welcome any and all advice

You say the LOAN was only in her name. Then somehow her husband's name appeared on the title. The title would not have changed just because the loan was paid off.

Here's the thing - when you have property and put the title in the names of 2 people as "John Doe and Jane Doe, JTWROS" (Joint tenants with right of survivorship), or John Doe and Jane Doe, his wife -- or John Doe and Jane Doe, tenants by the entirety (joint tenancy between married people), it acts as a testamentary substitute.

That means that both are owners and, upon the death of 1 of the "tenants", title automatically passes to the 2nd who will own property outright. This happens automatically without a will and passes outside any estate matters. It doesn't matter whether she had a will or not.

So you need to check with the dept of motor vehicles and make sure title was always that way. If it was, he is right it is his vehicle.

The only exception would be if title was placed as "John Doe and Jane Doe, tenants in common", in which her undivided 50% interest in the truck would pass to her heirs, and you would own half the truck. That would be a very interesting scenario.