JD used to operate with bitcoin but was closed in 2014 and later reopened with clams only because of legal issues. Details can be found on http://just-dice.blogspot.ca/2014/06/betting-and-depositing-disabled-on-jd.html
Apart from using exchanges and shapeshift, I have encountered some users on JD willing to make a trade. There is a built-in escrow feature on JD that you can use. Details can be found on FAQ page.
Trading on those plat forms you menationed will mean loosing a few btcs. Also how about the whales how do they do their exchange or did he just create the site for regular gamblers that gamble moderate amounts?
No idea. I only know that dooglus is a Canadian. I don't know if other gambling sites are based in Canada or if owners of other sites are in Canada.
I have made less than 5 altcoin trades on exchanges in the previous 2 years. I haven't lost anything from it, but at the same time I don't have enough confidence to recommend any exchange to you. No idea how whales on JD get their clams or where they bought their clams.
For the last question, I guess https://bitcointalksearch.org/topic/m.9772760 should be helpful.