Welcome to the Classic Forum from Minnesota!
You definitely found a project! For what it's worth, when I got my '83 gl1100, it had sat for 10 years. So, I pulled the carbs, the worst I've ever seen, and while working on them I soaked the cylinders with 2-cycle oil and turned the engine by hand each day a few times. Then I replaced the timing belts, reinstalled the carbs, and moved on to other jobs, and kept turning the engine a couple of times each day by hand, adding oil thru the plug holes as necessary. Just wanted to SOAK those rings so that if there was any rust or sticking of rings, I'd give them a chance to release and not score up the cylinder walls too much.
Once I was done with other stuff, about 3 months later, I just bumped the starter a bit a few times a day with the plugs out. Finally it was time to try an actual start. Started right up! And, it has weak spark, so this weekend I'll install coils, spark units, and a CDI that I just acquired from a guy in GA from another forum, plus dial in the pilot screw from 2-1/2 turns from bottom to just 2, which is the actual spec for that bike. Bet it runs fine and I'll bet the careful patience will yield results in terms of the compression readings. You clearly have plenty of patience!