1) I'm not aware of any organization focused on casino ashtrays. There are individuals like James Campiglia and Bill Judge (and I'm sure others) who know a lot about them. There are some super aggressive bidders on Ebay for very rare ashtrays and I'd imagine that these people have fabulous collections.
2) I'm not aware of anything beyond the Anderson book. It's too bad but it's a lot of work. I'd buy one.
3) No web site that I'm aware of.