Apparently your situation was different from what I experienced, and you actually did receive additional income in 2017, that was actual back pay. Wish I could help with that, but unfortunately I can't. The only thing I can note is that if you did in fact receive money in 2017 that was back pay for prior years, then technically your 2017 in isn't "artificially" inflated. It is inflated. But it's not artificial since you did receive the money in 2017, regardless of the year it was for.
You should be able to consult with base legal at your nearest military installation on this matter, and I'd be interested in what you learn. This time of year practically all base legal offices have additional staff specifically trained for military tax situations such as yours.
If there is an RAO (Retiree's Activity Office) in your vicinity, that would probably be the better place to start, since those folks would most likely be more knowledgeable in military retired tax situations.
I would expect there to be some provision where you can "spread out" the back pay over the next 10 years or so. But I'm not sure if the TTX program can handle such a situation.
