Dads In Critical Condition - What Do I Need To Prepare For When He Passes?

Location: Florida but his legal address is still Iowa

My dad is dying. If not now, fairly soon.

He is not married and has two kids myself and my brother. He has six figures (mid to high) in medical debt before counting like 10 maxed out credit cards and a few personal loans. He also has an insane mother.

Currently he was homeless prior to this ER visit so all his stuff I put into a storage unit in my name. It’s full but most of its junk by a normal persons standards. He owes like 70k on a car and owns a beater outright that’s worth about 2k.

My questions are:

Would Florida or Iowa laws apply if his legal address is Iowa but he’s lived in Florida for a few months just on my couch and in hospital?

Would I have to do an official probate if there’s no will (he refused to write one) and he owes so much money?

If my grandmother gets involved could she force me to open my storage unit to access his stuff? She did that to my cousins when my aunt died and stole all their mom’s stuff but it was a unit in her mom’s name and mine is in mine.

If my grandmother magically makes a will appear that shouldn’t exist which she’s also been rumored to have done, what should I prepare to be ready to contest that?

If I want to keep this car that he owes like 70k on would I be able to contact the lien holder with a death certificate and refinance it to myself? It’s his prized possession I’d hate to lose it.

Lastly other than social and birth certificate which I found in my unit, and a list of debts he has which I’ve also put together through random stuff in this unit, should I be ready with anything else document wise?

Trying to be prepared so I don’t lose his things like my cousins lost their moms sorry if it’s short