Yuk--anxiety sucks! But your grandson has his whole family on his side, and that is possibly the single most important factor that contributes to resilience.

There are plenty of people with autistic traits but not full-blown autism. Probably more people have subclinical autistic traits than there are with autism itself, actually. You might read up on it, just to inform yourself a bit; some of the same stuff that helps people with autism might help your grandson too, because of the similar cognitive style.