2002 Oldsmobile Bravada shaking and stalling

Shakes or Wobbles problem
2002 Oldsmobile Bravada Four Wheel Drive Automatic 93000 miles

I have a 2002 Bravada and have had minimal problems with it. However recently it seems that many random things are off. First thing I noticed was the idle was sometimes really low leading to stalling at a stop sign and in rush hour traffic, however if I switch to neutral and rev it's ok. Sometimes it idles high although not as often and only in neutral. The cruise control has stopped working since this started. Also when going over 50 mph and I start to brake the whole truck shakes. The other strange thing I've noticed is the whole back end seems a lot lower than it used to be. The frame is closer to the tires than I remember and the rear door used to be higher than me 5'3 and now I hit my head on it. Any ideas would be greatly appreciated!