Just got my first slant six

Welcome. Slants are cool. I also have a small-block and big-block car, and respect them all. Even my M-B diesels, though some of those owners are definitely autistic. One guy added a turbo to his slant and runs 1/4-miles in the 10's (youtube), which thumbs a nose at the continual "replace it" rants.

The low oil pressure might simply be due to gunk on the pickup screen. That is a common problem, and the gunk you see under the valve cover makes it more likely. An easy fix is to drain the oil and fill the oil pan w/ gasoline (safer is diesel or ATF) and leave for a few weeks to dissolve gunk on the screen. Best might be bio-diesel, and since in CA, you can buy a few gallons of Propel Diesel HPR which is bio-based and thus should be a better cleaner, or perhaps even cooking oil. To kill another bird, clean the top end w/ a brush and solvent, which will drain down into the pan. If your pan gasket is suspect, you might later remove the oil pan, and the timing chain while in there (and chain may have slack and need replacing). But do that after verifying the engine is OK. If you do go in deep, replace the O-ring on the oil pump pickup tube, since "sucking air" could also explain low pressure. Worn crank and rod bearings are the main mechanical cause of "low oil pressure", not worn piston rings, so doesn't necessarily go together w/ low compression.

A good sanity test on your compression readings is to turn the engine over by hand. You can just pull on the fan belt w/ 2 hands. If you feel it strongly resist you 3 times per rev, and must wait while you hear the air hiss down in each cylinder, then there is no way your compression readings are correct. With those, you wouldn't feel any resistance from such "air springs". When my 1969 Dart was worn, I measured ~70 psig in 1 cylinder and >100 psig in the other 5. So I agree unlikely that all 6 are evenly worn, so strongly suspect your measurements. I think your spark plugs would also look oily. My bad cylinder showed a perfectly clean spark plug, i.e. raw un-burnt gas flowing thru. If you truly do have low compression, it may simply be the valves need adjusting, which is a common task on these engines (solid lifters, not auto-adjusting hydraulics).