sump overflow return pump

Just finished setting up my first sw system. 75gallons with a 20 gallon sump. 9.5 mag return and ran into some problems with my setup. ( Newbie mistake ) I had to install a ballvalve off my return pump becuause I was returning more water than could be provided via overflow box. My initial...

I just bought a 55 gallon corner tank and it has a overflow in the back. I thought I'd plum the overlow and pump prior to adding the skimmer to check for leaks (used tank and sump). Anyway, I have a 3/4" stand pipe with a home made muffler (looks like an old water spiget with a 1/4" hole on...