It is my understanding that "Domo Arigatou" means "thank you very much" as either Domo or Arigatou on there own can be used as thank you. "Domo" means both thank you and hello. Leading to the hilarious pun in bleach wher Aizen says "Domo, Unohana Taicho" which can mean either "Hello Captain Unohana" or "Thank You Captain Unohana" which is hilarious in the context. Anyways I'm rambling.
Dono is (I think) something that you would use to greet someone who is very high up, but on a par with you if that makes sense. Or something, I'm no deadfire thats for damn sure.