How much amperage is the vehicle drawing (clamp amp meter on battery cable). And how much amperage is the alternator putting out?

How about at 1000 rpm? Voltage / amperage?

I got higher amperage/voltage by further tightening (the already tight to me) belt.

Also do a voltage drop test from the battery center terminals to various points on the car - engine ground at alternator, + cable at alternator, +at fuse block terminals.

Search google.com for how to do voltage drop tests on a car. This will find loose or dirty electrical connections including poor main electrical grounds.

Also what is the problem? Is the battery not staying charged? A fully charged battery is 12.75 volts with the car off. Is it not around that voltage after you drive it each time? And is it the super large Mercedes spec battery?