[gismo1554]

In terms of wait times, it really does depend on the attraction whether there is given a wait time or not I found. Also as said you will have your 3 regular fast passes. I'd be inclined to book one for slightly before you plan on arriving then the next two directly after each other to then allow you to do the DAS in between something like:

9-10
Plan to arrive around 9:30 so straight to ride
go get DAS return time
DAS return
11-12

That way you are still trying to minimise how long you are in the park. As others have said they can't legally look at proof of condition and too many people would abuse it if they allowed the rules to be broken. The DAS system itself will only allow you to hold one pass - I had an issue last year where one of my passes hadn't been used properly (the ride FP tap thing had broken so I couldn't tap to say I had used it) and the system itself had to be adjusted to allow me to get a new one. It was a big faff but its how they stop people saying they need DAS and then just rinsing all the rides. I also think its worth consider an ECV. The parks are huge and just walking them can actually cause more fatigue than you realise until its too late and you are stuck the other side of World Showcase. My sister has a hip condition and although she walks fine at home she can't cope in the parks even for a few hours so rents an ECV to make things easier.