Yes, it works on pretty much any ride - not the trains or Main Street vehicles, as luckyrabbit mentioned above. With that being said, the waits for Fantasyland rides can still get pretty hairy, even with
DAS, as they're accommodating both users with mobility issues and DAS return times. We did Peter Pan once via DAS and we still ended up waiting an additional 30 minutes after our DAS time, and it was in a small area surrounded by lots of other people waiting - needless to say, while my kid loved it, he hasn't been willing to do it again. My recommendation would be to try to get there for rope drop (if possible, I know how hard that can be with kids on the spectrum) and do all the Fantasyland rides first, then use FP and DAS together for the rest of the day to manage waits.
We have similar line issues. We haven't had to use DAS on our past few trips (combination of low crowds and MaxPass have been working well), but our line strategy is that one parent goes in front, kid goes in the middle, and then another parent stands behind him, so the kid is sandwiched between us. That way we can form a decent-sized buffer for him so he can have his space. The only places that get iffy are preshow rooms like the stretching room for the Haunted Mansion or the video room for Guardians - there we try to get him right on the edge of the room instead.
I'd be happy to give other tips or advice if you want - feel free to DM me!