Personally I believe the Director would appreciate knowing of the circumstances and responses from the three new staff members who do not "get" your kid. Going forward, other children may benefit, in addition to your own.
IMO, an adult who does not thank a child for gracefully given facts, is not a good role model. It appears the adult had an opportunity to affirm the child and create a bond, instead this staff member chose to shame the child.
Staff members may benefit from knowing that difficulty "hearing" can go beyond the mechanics of sound, and may include auditory processing.
Knowing which days your child may be without staff who know him seems like a great strategy to combine with a discussion with the director. If late arrival and/or early pick up are allowed and do not cause your child to miss a favorite fun activity, that may be a great comfort to him on those days.
