I have no advice, I wish I did, but I don't.
When you mentioned Camp Pendleton I had hope. I have learned that Camp Pendleton ITT is the best for getting DLR and WDW tickets (so much better than SOG), and was bummed to read they couldn't help you.
In the future, I would suggest calling them over your Texas ITT since it isn't close. FWIW, I ordered our WDW and DLR tickets last week in the morning and they were at my doorstep the next day (and I live 2200 miles away!)
IMO, it is ridiculous this ticket reissue is so time consuming and difficult. Your 6 salute tickets being reissued for current salute tickets doesn't seem like a crazy request. It honestly seems more crazy to only let you reissue as a standard ticket. Too bad common sense sometimes doesn't win.
However, with all that said, the big thing isn't the tickets, it is that your parents are cancer free!! I know you know that but I am so happy for you and your family they are. And to go to DL again is the cherry on top.
The ticket issue will eventually get figured out, even if it isn't the way all of us on here want it to go. No doubt, it would bug me to no end too, and I would have done everything you have to try and get things to work out. But at some point your time and sanity is worth more.
Enjoy your trip!! I know you will. Like you said, in the end the memory won't be about the ticket reissue. It will be from the time shared with your family in the parks.
(ps, I never wanted Disney to prove me wrong as much as this and you get a salute reissue the way it should be!)