Lets start with statement # 3
You say there is no power at all,..........,Does this mean that :
1. The engine does not have power ?
2. Power window, Power door locks,,radio,,lights,,,do not have power ?
3. I was going to ask if the starter had no power,,
but you said that the engine turned over when you turned the key,
,hey,,wait a minute,,how can the starter turn over and you do not have any power ?
4. You say that you pop the hood and and twist the battery connections and the truck fires right up,,,,,,
Then you say " I don't really know if that actually does anything ",,huh ?,,,well it MUST do something,,,because if you had not popped the hood and twisted the battery connections,,,then we know,,that would of done,,nothing.
It sounds like you need to replace the positive and negative battery cables and put the new ones on good and tight,,,,that just might solve 99% of your problem.