Lovely fish! In fact I was looking at that exact one and wished I could have bought him. Are you located in the US?.. because I would definitely buy a pair from you if you spawn him. :) I'm working on starting a marble line and would love to have fish like him!
You sound like you are doing the right thing by researching and are well on your way.
As for where you would sell the fish, forums are a great place to start! Then aquabid and ebay. You'll find that if you have good stock and price the fish right you should have no problem selling fry.
IMO I would get both sisters. They are both excellent. I like the first girl better then the second but they both would produce really nice fish with that male.
If you have any questions feel free to ask. I would really like to see you spawn (partly because you sound like a great candidate for a potential breeder and partly because I REALLY want some fry from a match like that