I will take a shot. I have been an coach of basketball and baseball the past eight years. Previously played at the highschool and collegiate level.
Your first point is valid if true. Making fun of a kid with a disability is out of bounds.
To the other statements. It sounds like a coach trying to motivate kids. Not everyone does that is a positive way. Sometimes that can't be achieved in a touchy Feely way. No disrespect, if your son is starting as a Sophmore, then that gives me pause. You don't mention what level of play 1a, or 6a. Either could have a Sophmore not be able to handle Varsity basketball on an emotional/mental level. Even if the physical skills are there. Younger players tend to run to parents when the mental side of the game gets tough. Usually the kids want their parents to fight their emotional battles for them. That usually ends with the kid quitting.
I am not saying this is a good coach. Over my years of playing and coaching I have watched parents ruin more athletes than coaches. The modern day coddling, egos, prodigy parents, and my kid does no wrong is hard to stomach sometimes.
I would suggest going to all practices. Observe for yourself what goes on. Teach your kids to be resilient. Teach your kids to work hard and take all criticism. It will serve them well when they get into the real world with zero rules!!
Good luck out there!!