Your choke issues are normal,the main body,metering block and bowl (unless needle/seat threads are stripped) don't go bad.Some play in the throttle shaft is normal and can be bushed if needed.The biggest problem I have found is bases not square by being over tightened,also an easy fix.From what you describe,I would check for vacuum leaks before I would consider replacing the center carb.If you are using the thin black base gasket and your base is not square,it "will not" seal.I did thirteen 6pk sets last year and six since mid December,very few had based that didn't need milled.
Good luck.