1) One AGSQL per domain, you must purchase an extra copy for each site.
2) Yes, we(my brother and I) install all of our own scripts unless we are not comfortable doing so or the script owner doesn't allow it.
3) I have a 88X88 thumb site, is pretty small and I dont recommend 88x88 at all but I am using Soul Cash hosted galleries on that one and they come with premade thumbs that size. That URL
Orgy Cafe
And you have already looked at
Slut Bunnys which is 90 X 120. I don't currently have a 120 X 160 thumb site going. I threw up a quick page that shows all three of the thumb sizes side by side so you could see the difference. It is here:
Thumb Sizes
We might have to start a new thread or GG needs to change this one to the "Auto Gallery SQL tutorial"
Seriously though, I never mind answering questions. So let me know if there is anything else you would like to know.