OK, very good. Then the next step is to strip the head and find out if it is warped and if there was a bad valve in #2. Keep the valves in order. If either is the case, then it is likely that #2 piston and rings are OK and that the issue was in the head. It is not 10000% guaranteed at that point that the #2 piston is OK but at least you would have found a definite head issue that would explain the low compression. Also, have the shop look at the head gasket to see if they think it was leaking.
Then get the report on head and guides and cost and decide from there on the head.
If NO head problems are found, then you can just risk that all is OK with some minimal head work and put it back on.... OR you CAN pull the #2 piston. (I've done it more than once...OK, twice total LOL) The oil pan has to come off (easiest out of the car but you can hoist or jack up the engine carefully and do it from underneath), then remove the 2 connecting rod cap nuts, and carefully push the rod bolts up and past the crank, and then the rod and piston on out the top of the engine. It'll take a bit of force to pop it past the carbon and ring ridge at the top of the bore. It is not easy to do in car with the crossmember under the engine. So most guys would pull the engine at that point.
But if you do find some evidence of the piston scuffed at that point, then what do you do? You can indeed put back in one new piston and ring set. You would hone the cylinder to get the rings to seat. But now you have 5 other worn pistons and worn bearing sets, etc. So your solution may be best; just do minimal work and put it back together. It was basically running and not exploding, right? It won't be worse now.
Hey, don't feel bad. We have all been there. It is an old engine and anything can be inside there. And the good thing is that the oil-in-the-cylinder test indicated that there was something in the head area wrong. Next time, slow yourself down and do an air pressure test in the cylinder as a extra step; that would have shown right where the problem is. That is why mechanics do that extra step.
FWIW, I would call those cylinder 'scratches'. Those are not at all uncommon. A scuffed piston is one where it has overheated and expanded to the point of rubbing the cylinder wall hard, and getting so hot that the aluminum in the piston softens. When it cools, it will then shrink to under normal size and will rattle in the bore. The cylinder wall usually shows some broad darkening when that happens and often some bits of embedded metal from the piston; I don't see that here. That is why I think you ought to keep on with the head investigation.
As Red Green would say, "We're all pullin' for ya!"