That uneven knob wear is common and happens because the deep lugs allow the lug to drag such that the front edge wears more than the back edge (like dragging a big eraser across a table top, it bends and the front edge gets worn off). The best way to even that out is to regularly cross rotate the tires at 5k intervals.
One way to figure out what might be going on with the vibration is to get someone to drive along in another car and have them observe (and video) your front wheels at the speeds at which the vibration is happening.