Ellie is Miss Wiggle Worm at the vet's office. She does get very nervous but then again, if somebody yanked my teeth out, pulled things out of my abdomen and always poked my neck to get blood, I'd be upset too.
We do take treats occasionally for the vet to give her.
If you can't get him calm, you may be able to use Benadryl but it doesn't work for all dogs. If that doesn't work you could go with something stronger but your vet would have to prescribe it.
Taking them to the back for procedures is very normal.
That's just the way most places do it if a tech needs to restrain the animal.
As long as you don't think your vet is trying to hide something and you trust him/her, it sounds okay to me.