Emilios,
The Cultural Centre project may yet come to life, so maybe we eventually get to meet.
Compression should not need the throttle open. Adequate air supply will get to the cylinders for the test. Otherwise, our engines couldn't idle.
100 psi does not indicate a broken piston, and firing with that compression imbalance would not lead to "huge" vibration. Running on one cylinder, in my opinion, also does not lead to "huge" vibration, but is easily checked by pulling one plug wire off while the engine is running and feeling the difference. Compression problem sounds like one of the following: gasket leak; valve leak; ring leak; test method error. To test for ring issues, shoot two or three squirts of oil into the cyclinder and test again. If the rings are at fault the compression should rise.
I am thinking you did not find engine or head-steady bolts to be the problem, or you would have told us.
If it's a broken crank, as far as I know, the engine isn't running.
Is there noise in the area of the crankcase? When I lost lubrication to one rod journal (in 2007), the bearing spun and the rod became very loose, but the engine kept running. Plenty of vibration. I think, you could get different degrees of the same problem that result in even more vibration. Here is the video I sent to SRM for help. They replied, "Don't start the engine again before a tear down." Lifting off the barrels exposed the loose rod right away. Anyway, eliminate the easier and more accessible possibilities before tearing down.
http://www.youtube.com/watch?v=T9grUuIEzM0Richard L.