This is coming from a USAF pespective as well, so take it as you will. I went through primary as an AF guy flying the T-34C in Pensacola (good times!) and watched numerous USN and USMC guys not get the fixed wing. At that time (1998) I would say it was more like 80-85% were going helos. I think the 60% is really low.
Fast forward a few years...when I became an instructor in the T-37 and T-6 I watched numerous Navy and Marine students get their dreams squashed when they found out that AF training didn't guarantee a fighter slot. It is a very small percentage that get fighters.
If you follow this path, be very prepared to not get your dream slot. Your first priority should be to serve your country in whatever capacity it needs. I have had several times when my career didn't go to where I wanted it, but it was where I needed to be. UPT instructor was one of them. With that said, I went in with an open mind and it turned out to be the best assignment of my career.
Like others said, I think we are pretty far off on the F-35 being full up. Good luck with your decisions!