[Oddsock]

Does he have things like kongs, to eat his food from ?

Caleb at times eats fast, putting his food in a Kong or other similar toys (he has several types), slows him down. He either refuses to eat or eats fast when stressed...then chokes and throws it up. Kongs slow his eating down and give him something else to focus on.

P.S Also does you son make a fuss of him and say goodbye before he leaves? This can make it worse. Ignoring him for a little while before leaving, and just walking out, can lessen the stress for some dogs.