1926 Credenza: you covered everything, and quite well!
I use Tungstones on my 10-50 as I've said many times before. The real key to a long life for one as well as for your Victor records is to only play Victors that aren't really trashed. You're spot on about other brands of records, they don't seem to deal well with many others, but then I've got some nice Brunswicks and VT Colubias in my 10-50 (all dupes I keep just for these machines) that have held up just fine. Put a disc on that's already got worn grooves and you can watch the Tungstone stylus dig right in and tear it up even further.
I've got the exact same Everplay box and needles you have, Gramophone78, mine came very cheaply off Ebay several years ago and has 8 (9 if you count the one I opened) needles and a bunch of order forms and promo fliers. I use an Everplay that I opened up on and off, been using the same one for 5 years, in fact. I really like it, same tone as a half tone steel needle in my experience. I've never tried it on anything but my 10-50, but it sure sounds great on that when I put it in and it's perfectly gentle on 78s. The only caution I'd mention about the Everplay is making the tip too long, if you do that, they bend and you have to snip it off and start over. I only had to do that once. The card they come mounted on suggests using the thickness of the card as a suggested legnth for the point.
Anyway, my $.02 here.
Sean