ESAD is an admin. here on the Z. He would be the one to give you the info to start a local chapter if that's something you're interested in doing, so I would shoot him a message, and DSM is Deep South Mopars, a club affiliated with the Z, that has chapters all over the south. I'm a member of the DSM, New Orleans Chapter, but you should contact SRTAndy to see if you can get joined up with the San Antonio group, as that would be the closest one to you. They have meet and greets/get-to-gethers, things like that which I'm sure you would enjoy.
That's a good question, but I suppose you could contact ESAD for details on how to get something started. In the meantime, I see you're not far from San Antonio. Have you considered joining DSM - Deep South Mopars, a club affiliated with the Z? They have a chapter from San Antonio, and, if you're interested in that, SRTAndy is the chapter president, so he would be the one to contact for that. You can find Andy on here, so shoot him a message, I'm sure he'd be glad to have you! As far as decals, I don't think the ones for the Ram Z are available anymore, but, there again, the DSM might have something for you. Feel free to ask if you need more help, but that's where I would start!