I just posted a link at pro-touring.com, I think they'll enjoy this.

In terms of getting title to the car, your best bet is probably to give his mom a call and see if she's interested in signing over the title to you.

That way, you avoid any further hassle, and she avoids:
having a lien placed against a car that she owns,
being dragged into court with her son,
the costs of hiring an attorney to deal with all of this,
any possible damage all of the above might do to her credit rating.

It sounds like she's a pretty decent person, and odds are, she's a little overwhelmed at the moment, so if you can get her to sign over the vehicle and make all the problems go away, she might go along with that.

Of course, if there's outstanding financing on the vehicle, that adds another layer of negotiation, but starting by offering to make it all go away if she hands over the car might be a reasonable and inexpensive approach.

Good Luck!