It's a semantica argument.
Development-al, as in, it's a physical development issue that puts people at a disadvantage - I'm partially deaf in one ear and it does, indeed, put me at a disadvantage when I can't hear what the person next to me is saying, versus someone who can.
Not develop-mental. I don't think that anyone who really counts would argue that someone who is deaf is automatically mentally disabled. People lock onto the "mental" part of the word, and not the "develop" part of the word.
People may not want to hear it but yes, in some (most?) situations it can be considered a severe disability because you are living in a world where the vast bulk of people can hear and see normally.
To address the list you put up:
-if a person is born deaf and happens to grow up in an area whose school district doesn't have anyone who is ASL proficient and their family cannot afford it then yes, they are at a disadvantage for learining because they cannot hear what teachers are saying. They can read just fine, but they are most certainly at a disadvantage. If they weren't, then ASL wouldn't have been developed. This education deficiency directly effects their income capacity and thus their ability to live independently, self-care, self-direction, and, it could be argued, their self-care because it puts them at a higher risk of being at an inability to care for themselves.
-in terms of mobility, perhaps less so for the average deaf person, though our sense of balance is directly related to our sense of hearing, most deaf people do just fine.
So while the impact may not be as severe as someone who's parapeligic in some ways, in other ways, it is more severe - a parapeligic may still be able to communicate verbally without speech and pronunciation issues and thus be more successful in a career in the public sector, like law or politics. A person with severe autism may be unable to adequately survive on their own due to their inability to do some basic maintenance-related tasks (which a deaf person could do), however they would be able to work as an engineer on a construction site, whereas a deaf person could not, since they could not respond to audial warnings for their safety.
It's an ugly truth but it's a truth, and I think that people are better served when this is addressed head-on as part of their being as opposed to fought tooth-and-nail over semantics.
I'm tall and I have exceptionally large (size 15 double-wide) feet. I can't drive some cars, I can't find most shoes easily, people step on them on busses and at shows, and it sucks in many ways... but it'd be harder and thus suck more if I knowingly bought a pair of size 12's that looked cool and got a car whose pedals were too close together for me to operate.