Since the lease was with both then you need to make the check out to both, to do otherwise would be making a legal determination which is what the domestic court is for, and where they can take their issue to resolve. 

At which point am I legally allowed to relist the property for rent again?

Legally speaking, if you have agreed to an installment sale, I'm not sure if the stepped-up basis is applicable.

Is there any legal guidance suggesting I can or cannot do this?

Here is a reference that explains:https://www.nolo.com/legal-encyclopedia/intestate-succession...2.

You will find many recent posts from investors who have lost all of their syndication investment, and then talk about bringing legal action against the syndicator.

Like most states, Georgia gives you the legal right to enter for inspections, repairs, or showings.

This should not be construed as tax, legal or financial advice.

Should I first consult with an attorney to discuss my options, or can I move forward directly with legal action?

Have your attorney send your contractor a letter explaining your dissatisfaction, any legal, ethical, or moral violations his operating methods result in, and making him an offer BELOW your “target” amountbest of luck I have an attorney that I considered speaking with on this matter, but I’m not sure that he specializes in things like this.