Have you removed the breaker plate and inspected the centrifugal advance system? It sounds like you've got some broken or missing springs on the advance weights. You should be able to turn the rotor a few degrees clockwise against spring pressure, and it should return to the same place every time you do that. The angle of the gears on the distributor and the camshaft keeps the gear pushed one direction while the engine is running (up, I believe) so vertical play isn't an issue unless it's really excessive.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!