Car still dies after battery, alternator & belt is replaced

I have a 2013 Kia Rio LX.

Initial trouble: Battery light came on and I immediately replaced the battery. A few days later, the battery died again. I tested the alternator voltage and received about 11V. I replaced the alternator. I also replaced the serpentine belt somewhere in there and that did nothing to help.

Trouble Now:

All new belt, alternator, battery. All correct parts (triple checked).

My car won't turn on unless jumped and it dies the moment you take the jumper cables off. Does having a dead battery affect what voltage I'll be receiving? How am I supposed to test the running voltages if my car dies the moment the jumped cables are off?

If my car is running on jumper cables, I notice that my battery light only comes on if I rev the car up past 3000 revs. I've heard this may indicate a loose belt. Anyone have any experience with what this may mean?

I haven't been able to determine if the multi-fuse (125A/80S fuse for the Alternator/Motor Driven Power Steering) is blown by looking at it, but I ordered one anyways (comes in on Tuesday).

I have checked these connections: Terminal connections (brushed them off), Connection to the alternator from the battery(pristine), plug to alternator (appears to be fine).


Going forward:

I plan on replacing that fuse, checking voltages, and doing whatever you guys tell me to do. Should I be unwrapping the wire that goes from the alternator to the battery to inspect? Should I be checking any other fuses? Is there any area that I haven't checked into that I should?