Made some progress on my tank.
I ended up replacing the pvc pickup with a 36" steel one and put a 45* end on the suction side.
I got the vented fill cap on. I did not anticipate the center not being a 2" threaded hole. Shame on me for not paying attention. So I have a 1.5" bung to pick up yet to cap it.
I also replaced the drain that was leaking with a new one with a ball valve instead of the screw-in/out type. No more leaks.
Tank needs a wash yet and resprayed with some white paint.
Im still not sure about the platform. I ended up using that 4x8 sheet of plywood for sizing and then the drain leaked. I think I might frame in a 4x8 space and fill it with rock. Not sure i am committed to its location so I am hesitant to pour a concrete pad.