vacuum advance issues

[Erratic67]

I changed my dist. cap, rotor, control module, and adjustable vacuum advance module on my Chevy 350. My advance vacuum module was bad so that's the reason for the change, other parts were for a quick tune up. I had no problems with a rough idle or backfire before the changes, all plug wires and firing order have been checked and verified to be correct. I followed the instructions for the new vacuum module when installed by turning it counter clockwise until bottoming out then installed it, I attempted to turn it clockwise as instructions indicate if problems exist but it does not seem like the allen screw is turning. I've disconnected and plugged my vacuum module but no change in performance either. My tach. is very erratic and sometimes not indicating RPM's either. Could all my problems be due to now having vacuum before and now having it?
Do I now have to reset my initial timing?
How do I set advanced timing in correlation with other timing?

Any help on this matter would be greatly appreciated as I am clueless at this point.