I am not Squidd, but I have been doing this a while.
OK, couple of things:
First, I would get rid of the mantis shrimp (cool drawing BTW)
Next, I have basically the same setup in mine. Just that I don't have the baffles between the cump chamber and the fuge. No real need IMO. Many advocate having a seperate inlet to the fuge for unskimmed water, but as long as your skimmer pump has a lower flow rate than your intake, unskimmed water will make it in there just fine.
Use a PVC ball valve and you will be fine. I'd also add one on the return line. Not really needed, but nice when cleaning the pump so you don't have to lower the tank volume.
Overall a good design.