[Cooper]

Some info of my .02 $. Again my opinion, not fact.

Oil, I use whatever cheep universal tractor/hydraulic oil, same stuff I use in 1:1 equipment. Been three years in the toys and no problems.

Pump speed, they don't need to be screaming fast. Some people add radio mix to turn up pump speed when radio stick movement is applied. I originally did that, lost all radio settings and didn't want to go through all that programming again. Have pumps on switch then controlled by dial pot to up or down pump speed when I want to. One things with pump and esc is you don't want pump starting from dead to whatever you want but rather have it running like 30% then up to where you want. Reason is that it's more hard on pump motor and esc to start and stop frequently rather than to be running and change speed.
To slow functions (be more smooth and realistic) like said above, adjust end points on servos. That will allow valve to only open so far, impeding volume but not pressure. You get slower movement but still have force.

If you have air in lines movement may be notchy or erratic. If very poor movement you may have a cylinder seal compromised allowing oil to bypass inside of cylinder. Most of the time it's the cylinder seals and not the valve seals. (Unless valves have been taken apart and not working correctly. ) if cylinders drift, valve is not centered.

Depending on what system you use the pressure release valve only comes into use when cylinders are maxed out/in on stroke. Like in the 4200 the 4the valve acts as a bypass. Other systems not having the bypass valve (less complicated) use the prv when idle and when max cylinder stroke. (Or if you hit a big rock!! ). As far a digging force, I'd say if you are able to drag the machine around that's too much. It's a wise idea to get a pressur gauge and actually see what your at. It can be removed after set up.
In my opinion not having any manual is better, then you don't know what people say can't be done and you find a way to do it!!! Necessity is the mother of invention!! Desire is the fundamental of learning!! Lots of good knowledge on this forum, just keep asking and have fun, they are addictive!!!