This is all good info. The glow plugs, for practical purposes, draw as a controlled dead short. Cranking a cold engine draws a lot of power, too.
Given winter temps in PA, your glow plugs could be firing for 2-3 minutes.
I suspect that your short drive is simply not long enough to replace what you've drawn down.
A daily drive around the block may be in order.
All you symptoms could also indicate a bad or insufficient connection hindering the charging process.
Regardless of what you find, I'd take a careful look at the condition of the electrical connections, at both ends of every cable, and make very sure the terminals and connections are clean, bright and properly tight. If the truck has the original, or even an older, battery and starter wires, flex every inch of them looking for an unusually flexible or "crunchy" feeling spot. Sometimes them corrode in mid cable. Don't forget to look at the studs on the buss bars etc. Sometimes they are corroded and get overlooked as a possible source of resistance.
Good luck.