I know what you are talking about with the shaking. above 50mph some things shake in the car. In mine, the passenger seat shakes (if no one is in it). I have had all the wheels rebalanced and it still shakes. The steering wheel is fine at those speeds, doesn't shake, so its something else. I also had my U and CV joints checked and greased when i had my alignment done in June.

sorry i'm not much of a help for the problem.