First of all congrats on the car!
As everyone has already mentioned, many items are typical wear and tear that were neglected by PO.
The only item that is of major concern is the oil consumption. You mentioned the mechanic did a compression test. If he did then he should have provided you with the pressure readings for each cylinder. Post those numbers and maybe a tech can check them to insure it's correct.
The parking brake is a simple adjustment, the spheres are not too expensive and can be a DIY if you're handy. The belt could be a tensioner or any accessory, you'll have to isolate that but it's not a big concern either.
Forget the PO and the mechanic, doubt you have recourse with either of them. For LA area members can you post the mechanics name for future reference/avoidance.
02 C32 AMG
84 190E 2.3 5 Spd