Electrical Problem

I have an electrical problem. I've done a ton of research, but I have limited knowledge about vehicles. I may have narrowed down the possibilities, but I don't really know how to test the theories. As I was driving to work during the day approximately two weeks ago my truck flashed the abs, passenger airbag and battery light all at once. Battery light didn't stay on, but when I turned my car off, it died completely. I got a jump, and it made it maybe 500 yards before dying again. Long story short, I replaced the battery and it ran just long enough to have my alternator tested. The guy at O'Reillys said that my alternator wasn't putting out at the time. Of course my battery light was on. I replaced the alternator, and it ran fine for a few days before doing the same thing on my way home from work. All the while the voltage meter was going up and down and my lights were going dimming etc. Then the same lights flashed and I made it home on my battery. Now my battery light is staying on again which I would assume means the same thing, but I'm not entirely sure? I've narrowed it down to a few possibilities, but I dont know. #1. The negative battery cable. Which sparks like crazy both when you first connect the battery cable and when you try to jump it. #2. I've also been hearing a vibration behind my gauges. That is something that was replaced before I bought the truck. I believe it's called the instrument cluster. #3. The wiring to and or from my alternator which supposedly the red wire sometimes gives people trouble. I really have no idea. I also checked my check engine light and it flagged for either the thermostat or some sort of coolant sensor, but the parts store couldn't tell me which. I guess my question is simply how do I narrow this problem down without replacing a bunch of things that don't need to be replaced. I don't trust putting it into a shop around here, and I'm certainly intelligent enough to try to fix it myself with a little help from a few mechanically inclined friends, of course. Unfortunately I've recently moved, and they would have to travel to help me. So its important that I narrow it down as much as possible.