I didn't read all of this thread, but for what it is worth, my $0.02 of experience is this:
I tested Dry Nitrogen versus "air" from my Emco V-twin 80 gallon garage compressor with no air dryer - I just drain the air tank (and the mounter's "tank") of obvious water before I do anything with compressed air.
Result? Tires vacuumed down against the wheel and then filled with nitrogen, versus compressed "air" from a tank that was drained of obvious moisture before filling the tire? No different. 30 cold built to 38 hot in both cases.
And that's when I stopped messing with the hassle of vacuum-ing and nitrogen-filling forever.
If you are getting significantly more pressure rise with "air" than nitrogen, it means you have significantly wet "air" at your inflation source - whether that is Krazy Frank's Tire Emporium, the Hoosier truck, or your own compressor.
The Nitrogen molecule is larger than "air" and thus it can still be a good choice for reducing leakage in long-term fills like lawn mowers, trailers, etc. But, in the end, I found Nitrogen to be a real pain in the butt versus just draining my tank to achieve "dry air".