.: Is it legal, per the IRS, to rent my primary home back to myself? 

if you have no money to put down then you're not ready.here's what i would do instead:-save up enough until you have enough money to do a live-in flip-do a live-in fliphope that helps

But yes, now that we are here, maybe let him know that if things do not get up to date or cleaned up you will go to his superiors.When people are late right at the beginning, I let them know that the behavior is not acceptable and let them know there are consequences to that bad behavior. 

They might be willing to give different terms especially to a high net worth person that they can likely make money on cross selling.

Like @Jesse Rivera mentioned above, I also go to a few sessions but spend most of my time in the lobby or at the bar making connections."

Cant speak for Nashville, but nationally Redfin recently released a report on their own transactions (they can see both sides of it) that average commissions have risen.This is no surprise to me as I predicted this would happen far in advance of the settlement.

Seeking insight from the community on converting a STR (primarily Airbnb) to long-term rental.

Do that before you spend any energy trying to kick him out.If he hasn't paid rent, you can call the police and have him escorted from the property. 

Also, if you focus on the fundamentals of the real estate, particularly with SFH's the cash flow is truly secondary to other benefits.

In fact you make yourself a bigger target for lawsuits.