Wikileaks is an English speaking organization with no Russian speakers on the staff, why would a leaker consider leaking Russian documents there? They can't leak what no one sends them, which also explains the other two.
Assange hosted a show for Russia Today back in 2012, so he knows some Russian speaking journalists who should be able to lend a hand: https://en.wikipedia.org/wiki/World_Tomorrow
Assange hosted a show that RT acquired the first broadcast license for, I doubt he had much contact with RT employees for that show. And again, why would a Russian leaker consider Wikileaks over another organization full of Russian speakers?
Good point, but still, consider how simple it would be for them to get Russian speaking help, and how small an effort it is in comparison to the gain in publicity - if they got something, of course.
Why would they get something is the question? I doubt Wikileaks is that well known in Russia, most Americans have a vague idea of what it is already.