iTunes has a feature called "Complete My Album" which I've actually used once or twice......not sure why you haven't been able to do that and "subtract what you already paid" but it's out there in some capacity...or it at least was for some things at one point or another.
out of curiosity why on earth do you feel that HD is or was a more "consumer friendly" format? i was watching the battle and rooting for bluray the whole time -- i didn't EXPECT it to win (see betamax vs VHS) but i certainly was glad that it did. the only people i knew who were bummed with the direction things went were those who invested in HDDVD early on and were stock with a "worthless" collection/"had to rebuy"
The shirts were originally for sale at http://partyontheinternet.com/lofnotc_shirt.html -- it's saying that they're currently sold out though word on the street is that a few remainders have been sent to Amanda's merch company to sell through from this point forward...maybe they'll pop up there, shortly.