Most of your scenarios and objections are addressed in the Hyperloop whitepaper. Will these proposed solutions work? Nobody knows. Sounds like a prototype is in order.
As far as size for wheel chairs it mentions having a pod that could fit a car(a Tesla of course) so fitting a wheel chair shouldn't be much of a challenge, or for the smaller pod it mentions being over 6 feet tall and over four feet wide I don't see why you couldn't fit a wheel chair in that amount of space.