I'd have to agree with Willy on this one. I would be furious if I knew what you knew. Definitely read the details on the carfax and determine if there is anything they can do.
Side Note: Carfax doesn't really provide accurate information, only a piece of the puzzle. When I did a carfax on my current vehicle it was also vague like yours for the first 5 years. I requested the PO supply me with a VMI to determine the mileage history as well as service/warranty history on the car. This combined with previous service records completed the puzzle.
Also you never did mention if the mechanic that did the compression test provided you with numbers. This is imperative to determine if he actually did the test and if the engine needs extensive work or not.
If you had a choice would you return this car to the PO and ask for your money back or would you keep the car and ask for $$$ to cover unexpected repairs due to his dishonesty?
02 C32 AMG
84 190E 2.3 5 Spd