The one motor I did not touch the internals does start/run OK, but as mentioned before, it too read around 30 PSI.
This statement say a lot for me. The one engine you did not disassemble starts and runs OK, but shows compression readings of 30PSI. It is very unlikely that the engine would start and run OK if the 30PSI readings are accurate. So, I am feeling pretty confident this is simply a gage issue. You mention getting the other engine(s) running, but they smoke a lot. Are you running the engine in a test tank or just a bucket? It is tough to get the needle valves dialed in when running in just a barrel/bucket, so I’m thinking the settings are still too rich. You will need to get the high speed needle somewhat dialed in before attempting to make low speed needle adjustments. You can not make these adjustments with the engine in neutral, it must be in gear under load.
Finally, don’t take the readings/indicators on the twist grip sleeve too seriously, they are usually inaccurate. In other words, just because you can not lower the twist grip down past the "shift" range, does not mean the engine is not idling correctly. Do you have the throttle cam pick up adjustments set properly?
Finally, please be very careful trying to start, or doing compression tests with an electric drill/impact gun on the flywheel nut. You don’t want to inadvertently over torque the nut and damage the crank/flywheel tapers.
.
.