At the end of the day, regardless of whether the First Class is issued (with or without a "SODA" or waiver), the question the airline must answer is whether you can perform all the necessary physical tasks of a pilot in the aircraft they fly, including a number of emergency tasks such as getting emergency doors open and helping others off the plane. These go well beyond the standards of a First Class medical, and it is not at all clear from what you've written whether you can do that or not.
Further, the airline must take a very conservative position on this, since as a common carrier, they are held to a standard of "the highest degree of care humanly possible." If in someone else were ever to be injured due to your inability to perform some physical task in an emergency, they would be toast in court. That thought will weigh heavily on their minds in a decision on whether or not to hire you.
And no, the ADA does not help you, since that law says that they have to hire you with a physical disability only if you can perform the "essential functions" of the job with no more than "reasonable" accommodations, and resigning aircraft emergency equipment would not be considererd "reasonable."
So no matter what you hear here, you would need to talk to some folks inside the airline hiring process, and they are not likely to be forthcoming unless they know it's on a "not for attribution" basis. However, there are still a wide range of aviation job possibilities even if you don't get on with a 121 air carrier, so as long as you can get the medical, I'd say press on.