The answer to this question depends upon whether the settlement was made on the record. If it was and you have a final judgment based on the settlement, then the case is over and cannot be refiled.
More likely, however, the settlement does NOT appear on the record. In this instance, the case should have been dismissed WITHOUT PREJUDICE. If in fact the case was dismissed WITHOUT PREJUDICE, you can refile for more $$ and also against the wife.
The answer to this question is dependent upon whether your wife assumed the car loan.
If she did, then she would owe the deficiency. If not, the lender would have no legal right
to sue for a deficiency.
A collection agency can not engage in tactics that violate California's Fair Debt Collection Practices Act.
Including harassing phone calls like the ones you describe. You should retain counsel and have your counsel send a "cease and desist" letter to the collection agency. Once done, the agency must communicate with the attorney directly. Any deviation from this is actionable and you may receive damages, attorney fees and a restraining order preventing such further calls.
Your written agreement with the language you referenced will supersede the prior verbal agreement. Prior work done by the tenant can stay as it is, unless you agreed to put the unit back to its original condition.
This is a family matter, not a legal question.
With that said, typically an escrow does this work.
However, in your case if you are worried about your brother
you as the grantee should do the recording.
The way you explain it he has no title, but he does have debt.
Unless the lender's agreed to remove him from the loan.
Change of title does not relieve a borrower, unless the
lender agrees to a full assumption by the new owner.