I have that problem as well because I have really fine sand. I just moved mine up a little higher on the wall and that helped with the sand. I run 3 korralia 1150's on my 125g and that seems to do a good job on circulation
No I have them on opposite sides of the tank, 1 closer to the top so it agitate the surface and one about in the middle, both facing the front of the tank. Then the third is dead center on my back wall facing the front wall.
I'm not sure why you would want your PHs pushing water against the depth of the tank. If these are your on PHs, I would rather face the PHs out pushing water along the longer side of the tank to create flow over the entire tank and not just back to front.