Are you using the multimeter to measure current draw (across the fuseholder) with the fuse removed? That will usually narrow it down to a specific circuit circuit really quickly.

 

Actually, I was using the voltmeter as an in-line thing. I disc. (+) and I hooked it in b/n.

I couldn't find anything drawing significant power...

So i bought a fucking battery cut off switch for now. Works great.
I will update this thread in a couple months when i find the real problem, just for thread-sakes
<3

 

It's most likely the body control module or one of the door modules. They're notorious for going bad on C5's. I can't count how many of those I replaced when working at the Chevy dealership, lol. They usually get water in them from a roof leak/plugged drain. The BCM is in the passenger side floor board. Take your floor mat out and you'll see 2 latches on the floor under the dash, release them upward and take that portion of the floor up. You'll see a big box-looking thing, that is the BCM. Unplug all the connectors to that and see if the drain stops.