Egon and dxdx are giving you great advice on the sump design, so I'll keep my suggestions towards your pump...
Based on the first pic you posted it looks like you are planning on getting a Reeflo Hammerhead Gold? If so, I think that's way too much pump for your setup.
1.5" drains can handle about 1,400GPH each, so your max capability on two is about 2,800GPH.
A Reeflo Hammerhead Gold does about 5,000GPH at 6' of head pressure, so your drains are not going to be able to handle all that flow...the Hammerhead will overpower your drains and suck your sump dry. You will definitely have to go Mike Tyson on those overflow teeth, but in addition to that, you will need larger bulkhead fittings/drains if you decide to use this pump.
If you want to stick with the Hammehead, you are going to need to expand your drains to 2", and even at that you will probably still have to valve the pump back a little.
I would personally recommend going with a smaller pump (the Hammerhead is a gigantic beast). I would recommend going with the Reeflo Super Dart Gold that does around 3,200GPH @ 6' of head on 185 watts
or
Run one Laguna Max Flo 2000's in each sump (each Max Flo 2000 does 1,360 GPH @ 6' of head on 78 watts, for a total of 2,720GPH on 156 watts if you were to run two).
I personally prefer the idea of the submersibles since you don't have to worry about leaky seals and you have a redundant system (two pumps)...in case one fails, the other will still likely be going strong. If you go this route, you should still plumb your sumps together.
Hope that helps you avoid my mistake (I had a Hammerhead gold that overpowered the teeth on my three 8" x 12" overflow towers):
Super Dart Gold on the left, Hammerhead Gold on the right:
Super Dart Gold on the left, Laguna Max Flo on the right:
