2006 F150 XL Electrical issues

Okay guys...I am back here with a question. Right now, my truck is having some electrical issues. I went to start it, and it cranked over once or twice, then just went dead. It was acting like it had a dead battery. So, the first thing i did was test the voltage. 13.4 volts or something like that. More than enough, right? So i heard the starter relay clicking. Replaced that, still the same problem. So, i put a different battery in it, one that i know for a fact to be good. Same issue.
Now, i  notice some things happening to electronics inside the cab:
When i turn the key, to the on position, the radio takes a long time to come on, and sometimes it doesn't come on at all
The dome light doesn't always turn on, but will turn on when you flip the switch
The message center in the instrument cluster turns on the backlight, but remains blank
The gauges in the instrument cluster do a twitchy thingy
Sometimes the key in ignition dinger comes on, usually not
The blowers sometimes turn on, if the knob is on
Sometimes when i turn the key to start it, It clicks rapidly, sometimes it is a very slow click, sometimes it doesnt click at all. The click always comes from the starter relay.
Sometimes all of this happens, sometimes it just acts like it is completely dead.

Now for the weird:
I assumed that it could be the starter crapping out on me, but since it was acting like it had a dead battery, i put a jumper pack on it, and it cranked right over. as soon as i removed the jumper pack, it went back to acting like a dead battery. This is with a new battery that i know for a fact cranks over a vehicle much larger than this one.
Does anybody have any clue as to what would be going on here? i am stumped, and i am going to be getting my license soon, and would like to have my truck driveable

Just a side note: i have heard that the Anti theft system could be the culprit (something to do with not recognizing coded keys or something) But the solution to that is to drive it to a dealer...someone didn't think that all the way through

This truck has given me nothing but grief. Now i understand why not many people rebuild titles for cars that have been wrecked, and why cars that have been wrecked are better off being left in the junkyard.
Thank you to anyone that helps!

Check your ground point for the battery, sounds like a loose ground.

There is corrosion on the old battery, but the ground point(s) are clean. The ones that i could check anyway. From what i could see, the main grounding point is tight and clean.

How many CCA (cold cranking amps) do each battery have (old one and the known good)?

Are they at least 660? Interesting it works with the booster even on the known good battery. I think you can rule out a bad anti-theft. Maybe bad ignition switch, but a little early to tell.

Okay, quick update. i left the battery disconnected for close to 24 hours (to reset all the electrical systems) The appliances inside inside no longer flash and act like they are possessed, so that is a plus.
But, the message center in the instrument cluster flashes and reads TEST after the gauges are done twitching
The old battery has 1000 CCA
The new battery has 850 CCA

Another quick side note:
Sometimes, i have to cycle the key a bunch to get anything in the cabin to come on. Often times, the radio won't even come on.
Today i am going to attempt to drop the starter and run it up to the local Napa to mark that off the list of possibilities. At this point, i am just going down the list of things it could be. If that comes out as good, then i will start looking into the ignition switch i guess.

I don't think it is your starter.  Just out of curiosity.  Do you have another key for the truck?  Is it possible that your key is just worn and not turning all the tumblers? Do you have a bunch of "other" keys on the keychain?  Sometimes that causes quick wear on the switch.

A good check for the starter, does that model still have the solenoid up top?  Once you get your key where the gauges come on (run position). Jump the solenoid.  Your starter switch may not be sending enough "juice" to the solenoid to give it good contact inside.

for safety, please be sure you are in park and the emergency is set

Yeah I agree about the starter thing, I'm betting it's a problem with the ignition switch. I wouldn't bother dropping the starter only to find out it's just fine.

Just scrap the POS and be done with it

Seriously though, sounds like a computer issue or the ignition switch. Check the plugs into the BCM and PCM, as well as the ignition switch. See if there's any corrosion in there or a kinked wire somewhere

Found one thing- in addition to the starter relay clicking, the PCM relay is also clicking. I didn't notice it before, possibly because it just started or possibly because it was covered by the clicking of the starter relay. Heading to Autozone now to get a new relay.