Coupla tips:
Can't tell you anything about pressure relief valve spring or relief pressure, but you could use this example as a template: Assume the ball/seat diameter at about 1/4", that's about 1/20 sq in area, so if you push a probe thru the relief hole against the ball, and the ball displaces at one pound of force, then the ball/valve will bleed at 20 psi. Adjust as you see fit.
Thinly applied grease on the bottom sump gasket (as you've done) will ease future disassembly. Same trick works for the difficult-to-remove side cover filter cover.
I've always oiled (a few drops) the innards of oil pumps, to prime them. If assembled dry, could delay delivery of oil during first start-up. If top end is well pre-oiled or uses assembly lube, this is probably not an issue.