I am sorry you had such a bad night.
I usually give soft praise to my dogs in obedience. I get alittle more excited in agility but I am never shouting. Your right they are not deaf, They don't need loud commands or loud praise or corrections for that matter. I believe quiet to normal voice actually is better the dog needs to pay attention. Shelties in general don't like loud voices. As long as your praising her ,who cares how you do it. Sheesh!
The deal with the Rott at the end of class was probably Ellie reacting to your stress. Your frustrated and it goes right down to Ellie. You had a long day and probably had little tolerance for the stuff that was going on.
Hopefully next week will be better.
I would try and continue class with other dogs. Relax breath, don't try and be perfect, try and give her a bit more space from the dogs. The more confident(that you can do it, that Ellie will behave) you are, the more Ellie will follow your lead.
Me, I would kindly ask the non instructor to limit their chatter that I'm trying to listen to instructor and then ignore them. I would also ask instructor for clarification on how to do something if there isn't time at the moment take a few minutes after class. They should be there to help you. Praise your dog the way you are comfortable and if she yells at you tell her you don't like being yelled at and neither does your dog.
Remember tonight was a full moon. Just chalk it up to that.