Before you spend $500/hr.
I would pen one last letter, delivered by registered mail to said seller for $2 postage.
Set a deadline of 10 business days for documented proof of Title or steps to secure Title.
note at bottom of letter:
Pending cc:
Letter to File
Attorney
State Authorities below
Next, after deadline refer said tranasaction as a "complaint" to State Attorney General, Dept. of Motor Vehicles, Dept. of Banking, Insurance, Financial Service Dept. Most States have a website, where you can cut paste summary, attach doc scans, and a case file will be created and reviewed at no charge. This is not a lawsuit.
Engaging in sale of "untitled" property or fraudulent conveyance breaks numerous trade laws, dealer franchise obligations, state dealer licenses, and banking laws (if liens are incurred).
Might seem harsh, but will surely get his attention.
Be careful what you say in such a letter. You cannot say something like,
"If you don't do XXX (whatever it is you want to happen), then I will call the police (or file a complaint with the attorney general, etc)." As strange as this seems - and as right as you are in the dispute - this is extortion and YOU could find yourself in legal trouble.
I'm not a lawyer, but as P/R of my Mom's estate I was faced with recovering checks which were literally stolen from her mailbox (by other heirs, no less!). I was told in no uncertain terms by the estate's attorney that such a demand phrased like my example in the first paragraph could land me in more hot water than the relatives who stole the checks! As he explained it, extortion is threatening to do something to someone if they don't do whatever it is you want them to.
The analogy my attorney gave was that if I caught someone in my driveway stealing my car, just call the cops - don't
threaten to call the cops if he doesn't leave. If you
declared that you are calling the cops, that's OK - you just can't
threaten to call the cops if he doesn't stop stealing your car. It doesn't matter that he's in the act of committing a crime, and that you have every right to call the cops - it's that you can't
threaten to do it if he doesn't comply with your demand. Yes, I know this is sometimes an upside-down world we live in! Perhaps an attorney can weigh in on this - I know it was quite a shock to me when I learned this.
Realistically, would a crime victim ever be prosecuted for something like this? I would hope not, but stranger things have happened. In any case, it might make things more difficult if you have to sue the seller and he produces such an "extortion" letter and then tries to claim that he's the victim.
This is an example of why sometimes paying an attorney for advice is the best way to go (although you might not like what he says). Plus, sometimes the attorney can do things that you can't do - or in a manner that you can't.
Good luck - I hope you get this sorted out quickly and satisfactorily.