You'll get some oil out, but if you work with the cylinder vertical, and something holding the ram up, you shouldn't lose too much. Messy, yes. Complete unloading, no.
Yeah... one of the down-sides to using NPT elbows. It's made worse by the fact that you have steel on steel there, since neither the elbow or the bung on that cylinder are too forgiving. Give it three wraps of tape on the elbow, then install. Tightening an NPT fitting is a "by feel" kind of thing, in that you are not hunting for any particular torque, but you're hunting for the point where torque suddenly increases rapidly. Then you know you've taken up the slop in the taper, so to speak. Only thing that's critical here is that you can never go back. Tighten only. If you overshoot, and decide you need to loosen a half turn to get back into alignment with the flare nut, you better remove, clean, retape, etc.
2 cords an hour is a heck of a lot of wood! If you consider time to buck, move to the splitter, and split (all this machine does... too many folks just count splitting time), I'm sure I'm at 3 - 4 hours per cord.