Yes, but he also mentioned that the bolt backs out by itself which is a prime indicator of the recall. No, the '91 is not covered. If the dealer just kept tightening it without replacing the bolt, even while being aware of the service recall campaign, then there is your issue.

Basically, what you need to do is read here, then do a search for "3.0L crank pulley"... because we get about 1-2 people/month posting about this issue.

EDIT: I can already formulate a working theory for you...
The bolt has been backing out, and because of that, the harmonic balancer (crank pulley) hasn't been balancing harmonically. What I mean to say is that it's rotation hasn't been perfectly circular and it's worn out the sleeve and keyway. The wear, when left unattended, will eventually damage the key and your pulley now has nothing to make it spin with the crankshaft.

So, if worse comes to worse, I'd say you're out for...
[*]new crank pulley
[*]new key
[*]updated pulley bolt & washer
[*]anything you want to clear up with the timing belt since it's already apart (timing belt, timing belt tensioner, timing belt tensioner spring, water pump...)

Again, count your lucky stars if you have no damage to the crankshaft either. Reading that the bolt has a history of coming lose and all the dealer did was continually tighten it is appauling. They knew what would eventually result. They only put a bandaid on the problem so they could get return business when things really started going wrong!