Hi Jason, I have a bit more time now, no fun trying sound sensible at 5am
You say a "katate-uchi" is essentially an O-wakizashi, hmm, I have one here with a 59cm nagasa, just as easy to call it a short katana
As for the 1450,s to 1530,s window, not too sure, this is a good read http://www.nihonto.com/abtartsuebizen.html
I did say we over-catergorize stuff, but hey ho, here we go, take a look at no7 running into the Azuchi Momoyama 1573-1600 http://www.yamakawadojo.com/the%20japanese%20sword%20historical%20changes%20in%20shape.pdf
Ive read on Aoi a few times (as an example), that no kazuuchimono where produced Eisho.
As mentioned before, look at the sword quality before the mei, look for quality original bo-hi in these swords.
As you say, katate uchi were no match for firearms (introduced 1542), they where an auxiliary weapon, but as an Ashigaru, you would be glad to have one, just in case your matchlock got wet or something