I would go with 1" on the return and 1 1/2" on the overflow drain. 3/4" on the return is too much pump restriction, and I think 1 1/2" would be too much liquid head pressure.
On the pump return line, knock out as many 90deg elbows as you can... these cause quite a restriction as well. One instance I can see right off the bat is flip your sump around and put the return line where it can push straight up instead of going through those two elbows. Essentially, in the basement section, change the label on your lines.... make the red the overflow and the cyan the return pump.