I also have a chronic pain and potential fatigue issue. Disney won't change the rules to accommodate sadly. They won't look at proof of medical condition either.
Firstly, I looked at all the park maps and planned rides so that we weren't crossing from one side of the park to the other. I know most would say it's a waste to use FP's for as soon as it opens but this helped keep our times minimised for being in the parks.
An example:
MK - Opens at 9am.
I would book a Space Mountain FP 9-10am, I would head to Buzz and get a return time as we first got in the park then ride a couple of lower wait time rides, like People Mover and Speedway, then head for our Space Mountain FP just before 10am, after this I would head back to Buzz for our DAS return time.
Second FP would probably be 7DMT 10-11am. I would head round to Peter Pan or Winnie the Pooh and get a return time for one of those then ride 7DMT, I would then hope that PP or WTP return time had opened up and head there. After that I would probably get a return time for another attraction but would completely depend what you wanted to do.
I would book my next FP for 11-12pm and again look for the shortest and longest wait times of attractions near the FP. I would get a return time for the longest wait and try and ride some of the lesser time ones before the return time.
I hope that made sense. Last year I used Touring Plans and it was amazing. It really helped me to plan things and it also gave me approximate walking time between the attractions (you can choose the pace) and it also told me the approximate wait times we would have. It was a god send and I'm just about to re purchase it for our next trip. I think it's $15.99 for a year.
Was great for helping find hard to get
ADR's too x