Sounds like you are not original owner and did not purchase it used at that LBS. If you wish to have the problem solved, expect to pay for that service.
When front der. rubs 'pushing hard' in 54T ring, that seems to indicate possible flex in BB area. Try setting up pedals 90 degrees OOP and see if it cures the flex issue.
Just thinkin out loud . . .
Pedal on TWOgether!
Rudy and Kay/zonatandem