re: Any vets or currently serving have any advice on the PFT?

There are people that specialize in the 45 day prep. Where they lose 30ish pounds and drop body fat in 45 days. They don't workout outside of pft time. So in theory you're good.

Run further then 3 miles so 3 miles is your bitch. Until you learn a good pace take a watch with you so you can have something help you keep pace.

The sit-ups I've never had that problem so I have no advice on that besides maybe focusing on stretching that part if you feel like it's a cramping.

I found the more push-ups I did with ease the more pullups I did. I used to aim for 300 push-ups and sit-ups in a day. Just staggering them throughout the day when I could fit them in.

Then if you ever become essential personnel and they deny anything is physical wrong / physical therapy I recommend swimming it.