Thanks for all the advice! I decided to not respond to their email requesting help in dealing with the manufacturer. I'm done!
More than him being a con-artist, I think he's a narcissist. He definitely has a grandiose sense of self and sense of entitlement that he should have outgrown by kindergarden.
Zen, I have good records including photocopies of all the pieces I designed, as well as every email sent by them and to them, which includes a lot of the issues (including how much and when I would be paid) that would have been addressed in the written contract that I never received. I wonder if this has any legal merit if, down the road, I discover they're selling the pieces I designed? At this point, I think it's unlikely that they'll be able to pull their act together (find some other poor schmuck to manipulate into producing a sellable product!), so it may be a moot point.
I had the best ride today. I rode as slow as I could, which was new for me. I saw views I had never noticed before on my regular route. Where'd that horse farm come from? Never noticed that before! Didn't think about them once. My life is back!