Concrete Block Wall Has Ugly White Stains
Two things come to mind - 


if you have white stains, they might be a lot less noticeable on a
whitewashed wall. And a porous whitewash is more likely to stay put
than an attempt to seal the wall with paint.
Even without proper porous backfill, it  would probably be worth trying to drill some weep holes in the bottom of the wall, to relieve pressure.