I was granted
DAS for very similar reasons, that I wouldn’t be able to stand inline for extended periods without going to the toilet and because of generalised back discomfort when standing from a car accident.
I wouldn’t have thought you’d have any issues with eligibility since standing in a line is something that would be difficult for you.
The only thing I’d say is that DAS gives access to the Fast Pass line at a certain time, it doesn’t give instant access to the ride, you still may have to queue in this line, especially for bigger rides, for up to 20 minutes potentially. This wasn’t a problem for me, just something to be aware of.