I expect that you will be able to cure the engine run away problem by examining the cruise control and the throttle cable from the dash board as they attach to the throttle lever. You will have to just look at it and open and close the throttle lever until you see what is hanging up.
Your brake problem is a strange one. I had the rear brakes hang up like that one time on my 240D. I released the pressure by cracking open the fluid line at the master cylinder. Once the pressure was released everything was hunky dory. I expect that yours is something to do with the master cylinder or the H block that proportions the front/rear wheel braking.
Best of luck,