Yes it is
Yes they are when we was there it wasn't very crowded
There are elevators to get to all floors, so in theory everything is accessible. That being said, there are many tight spaces, and when they are busy it will be difficult to get through many of the areas.
Not all areas are wheelchair accessible. There are a lot of stairs there (though I'm not sure if there are elevators for wheelchairs because we didnt explore that option). Hope that was somewhat helpful! There would still be a bunch of things he could do but not everything.
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