'80 D50 2.6L won't start

[OCD Boss]

A couple of days ago I tried to start my truck and all I got was a "click". After a couple of minutes of inspection, and trial and error, I wacked the starter a couple of times and it fired right away. So the next day I went and picked up a new starter and installed it. All excited, I hoped in, and "click". A buddy helping me, loosened the bolts slightly, and gave it a giggle. Tried turning it over and it fired right away. So I turned the engine off, and tightened down the bolts. Went for test drive, and drove to destination about 5 minutes away. Turned it off, tried turning it back over, "click". Inspected wiring and everything a 5th time, and gave the starter a couple of taps, and it turned over. On the drive back home, the vehicle died out on me 3 times while in motion (but would start back up while still in motion, I never stopped). Then it finally died after pulling in at home, and that was the last time it ran. Since then, I have ran a couple of new of wires for some fresh connections, added the MSD 0.8 ohm ballast resistor, and put on new battery terminal clamps. My 2 big concerns at this point are a) why do I only have 1 wire coming off my alternator (blue wire in pictures 2 & 3) where there is a "t" connector and autozone is telling me I am suppose to have a second going "somewhere" and b) why my starter won't engage to turn over the vehicle.

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