Overflow and return help

[pitbulldrummer]

Hello all. I drilled my new 90Gallon with 3 1" drains centered on the back just below the top trim for a coast to coast or Calfo overflow and 2 1" returns,1 towards each corner just below the top trim. Im using a "Beananimal drain system" with 1.5" pvc plumbing for drains. I ordered a piece of 1/4" glass 47+"L and 5.5" wide which I will silicone in a V shape on the back wall coming up just above the bottom of the top trim so the water level will always be perfect. i will bring the returns through the back 1" bulkheads on each end into the overflow 90 degree up then 90 degree over into the water. The sump is in the basement below the tank its a 55G drilled and baffled for a refugium on one end skimmer on other and a center return area which I drilled a 1" bulkhead close to the the bottom. I plan on using a external return pump but having trouble figuring out how much gph I need or can handle. AND factor energy efficency!! Need prob 8ft of vertical head and 4 90 degrees using 1" pvc. Any help would be greatly appreciated!! btw gonna be a LPS/Softie tank