Would you recommend deadheading grape lollipop garden phlox before pruning in fall? If so how would you deadhead the plant? Also what are your recommendations on how to prune the plant for the fall?

Definitely, deadhead your Grape Lollipop Phlox this summer to help it repeat flower. Just below the flowers and above the next set of leaves, snip off each flower heads when they starts to turn brown. I wait until spring to do perennial garden clean up and then prune phlox back to the ground. Just be certain to add a little mulch around the base before winter to help keep the roots warm.