Charlie, I can't really help on the other questions, but here are a few suggestions for the saddle interior. Depending on how dark it is, you might think of using one of these two.
This is Testors Custom Lacquer Interior Tan for the bottle,
and this is Testors Model Master Leather.
I have also used "Make It Suede" Buckskin textured paint for tan interiors, and it is a little darker than the Testors CL tan, but I don't have a pic of it right now. If you would like to see it, let me know, I'll get a pic for you.