Honestly I would have no idea how much pedialyte to give.Is he drinking water? Perhaps you could just mix some in his drinking water.
I think you can do a skin test on a dog to check for dehydration. Pull the skin up like you are pinching it together between his shoulders, if it goes right back he is good if it stays tented for a couple seconds or longer he is dehydrated. Let us know how it goes with him,I hope he is all better soon
