@upliftinglove As a former Service member and APFT walker (and was 30 plus with a knee condition), for me it always came down to form. If you have time, just practice getting that speedwalking hip-swinging form. I passed the walk by focusing on sustaining that form as long as possible during training, and alternating a fast normal walk for the entire distance. IT IS GOING TO HURT IN THE BEGINNING!
Start with 30 sec speedwalking "sprints" and alternate that with the normal walking style for 30 seconds. Do that for the entire 2.5 miles. When that is easy, change it to 45 sec intervals and keep increasing intervals until you can do it for 3-5 minutes a time.
The right speed walking form will get you the speed and endurance you need, and you will be less sore after. It SUCKS training for it, but if you practice it regularly (all year round) then during APFT it'll be a breeze.
I learned it from an elder NCO when I was young and in shape. I never knew how he could walk nearly as fast as I could run. He told me if I was ever in his shoes. That the form was the secret. Paid off for me. If you can put in the work, you'll get it passed, and finish out retirement strong.
Good luck!