Sorry, I'm not great at dosing but bchgirl just posted the dosing info for this somewhere.
I can tell you Ellie is 6.8 pounds or so and her dose is 1/2 tsp., so that would answer your question for Chip.
Using Benadryl to calm a dog down on occasion is not going to hurt them and may be necessary in some cases if they get too stressed out otherwise. It's not much different than giving Ace for car rides but is safer. I guess I don't see the problem...
I mean, of course work on the anxiety issues but sometimes drugs are needed.
That said, I just gave Ellie Benadryl for allergies and she is pacing back and forth through the house barking at a lawn mower, so it doesn't work for all of them.