I wouldn't worry about pitching more yeast, you should have so much yeast in there already that the amount from another packet would not make an appreciable difference. As far as hop bitterness / flavor is concered, adding the dry hop is a good idea, that should add some extra hop flavor. it will mostly add to the hop aroma more than the flavor, but that aroma will also complement what hop flavor is already there and should improve your beer. If you like a lot of hop flavor, consider adding a hop addition at 30 - 15 min left in your boil and that will add more flavor than bitterness.
"let me be the first to welcome our new insectile overlords"
On deck: Breakfast stout
Secondary: American Pale Ale
Kegged: Imperial red ale, Breakfast stout, Chipotle Irish red ale, Biermuncher's C3C cream ale