One screw with drywall anchor is sufficient.
Not a lot of good options if you can't fish through the wall. Maybe flat wire and paint it the color of your walls.
Yes, they are triangular in shape. If you build stands, just let them sit on the flat surface. They aren't going anywhere.
Regarding building stands, I read the manual on the 52s and it suggested mounting 5ft high. Will i be missing alot by placing on stands on side in back of couch and pointing them towards center of room? Pointing towards sitting position would send one side of sound to the back wall.
I plan on attempting a 3' stand like this, i think making this would be easier than mounting on wall and trying to conceal wires.