I would get rid of the relief valve that you have the gauge connected to.Unless yours is really solid, you will probably find that it leaks and you will lose substantial pressure over time. And as suggested, between the lid ad the quick connect fitting, put a valve inline so once you achieve the pressure, you can close it and disconnect the compressor.
As for shelfs.. I cut 3 9" dia 1/2" ply disks. drilled approx a 1" finger hole near the edges in each then dropped 1 down into the bottom of the pot. on the other 2, I cut and attached 4 legs that are approx 2-1/2" long. This basically gives me 2 shelves and a top piece that will difuse the incoming air out toward the sides instead of going straight down into the mold.