Don't be too quick to condemn the rings. The oil should have made a noticeable difference in compression if the rings were the problem, as it would temporarily improve the ring sealing. I believe you've got valve problems, either tight clearance or sticky or burned valves.

First of all, loosen all the valve adjuster locknuts and back the adjusting screws up about 1/4 turn counterclockwise. Right now, exact clearance isn't critical, just be sure there's some free play with every valve closed. Soak the valve stems with penetrating oil like Liquid wrench or KROIL in hopes any varnish or other sticky stuff will turn loose. Once the valves are opening and closing freely, recheck the compression. I think you'll be surprised. The one VERY low cylinder might have a burned valve, but the rest should improve considerably.
Jerry

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