Success! Miles4sale.com miles came through and they posted today and I got my Virgin UC award on my dates of choice next August/September.

Lessons learned:

1. Delta will not loan a single mile
2. Miles4sale.com lets you buy miles above the miles purchase limit on the Delta website (don't know how many you can buy, but they're so expensive I'd use only in a pinch)
3. There are some very helpful Delta reps
4. There are even more very helpful FTers without whom I would not have been aware of the upcoming reward changes on Virgin or my other options!

Thanks again to all.