Mrs, Mrs & Mrs
The Honorable Judge Smith and Mr. Smith for the envelope and Judge Smith and Mr Smith for the letter.
"Dr and Mrs Smith" is the correct salutation. (With Smith replaced with the correct surname)
Rabbi and Mrs.
Yes.
Dr. and Mr. Smith.
Dear Mrs. Obama,
Dear Mrs Ambassador..
probabaly just a mrs. would suffise
"Your Honor" or "Mr. (Mrs.) Mayor"
Dr. Smith and Mr. Smith separately..
Mr and Mrs would be proper. Attorneys are typical written to as Mister.