Sorry to hear you felt the CM was rude, but there are very, very, very few places to sit down at WDW and they remove more of them all the time. They recently removed the planters/seating in Tomorrowland over by Space Mountain as of last month.
I have trouble standing long periods of time in line.
DAS won't be able to accommodate your issue because no matter what, you're going to be standing
somewhere at WDW
, unless you are sitting on a toilet or at a restaurant LOL. Most of the outdoor seating at restaurants now requires that you be holding a meal (and yes, the CM's do patrol the area now!) You can't sit down on the concrete anywhere for safety reasons, and yes, the CM's do patrol the park asking people who are seated to stand back up. DAS provides you a way to stand off to the side of the actual queue and not be considered line-cutting if you jump into the line closer to the loading areas. The CM was correct in that you need to bring your own seating, whether that be a wheelchair, a rollator, an
ECV, etc. Camping chairs and portable chairs are not allowed at Disney as per park rules, so that leaves you with renting/bringing your own mobility device.
I am certain that if you told your doctor that you were planning to spend 8+ hours on your feet on a hard asphalt surface, walking averages of 8-10 miles each day in high temperatures and humidity, they would agree that a mobility device (used in short bursts/periods of time), would be much more preferable to the pain and damage you will cause yourself.