Your gallons per minute is determined by the displacement of your charge pump, the only to way to increase GPM'S is a separate dedicated hyd. pump.
Your systems pressure is determined by the shims of your implement relief valve if using the charge pump, or your system pressure relief it using a seperate hyd pump.
Engine:
Its difficult to determine if a cylinders rings "didn't seat well" its possible the engine didn't receive the proper finish honing, or the cylinder was oversize, or the ring gap was not set properly, or synthetic oil was inadvertently used
during break-in or the breather cover was not assembled properly are just a
few reasons for abnormal oil usage after assembly.
Balancing your rotating assembly will not normally be noticeable at normal governed rpm's of 3600.
And it is not recommended to go much over that as going 4000 will get you into unsafe territory with a stock cast iron flywheel.
When they blow up it ain't purdy what the shrapnel will do to human body parts, or metal parts for that matter.
A 3 spool valve is a handy addition to your system.
just some things off the top of my head to help.
Luck!