It is proper to address Mr. John Doe PhD as Dr. John Doe. You might also address Mr. John Doe PhD as Mr. Doe or Doctor Doe, depending on which reference he prefers.
Master John Doe
That's fine, or The John Doe Family.
The proper way to address that letter would be "Mr. and Mrs. John Doe."
Mr John Doe and family
The name followed by Jr For example: John Doe Jr
The general rule is to place a comma after "PhD" when it is used as a suffix after a person's name (e.g., John Doe, PhD). However, if "PhD" is used in the middle of a sentence to describe someone's credentials, no comma is needed (e.g., John Doe has a PhD in Economics).
If the Pastor who is the third and not a Junior is the only Pastor then you address him and his wife: Pastor & Mrs. John Doe. If all three were Pastors then you would address the letter as: Pastor John Doe,III & Mrs. John Doe.
When address to a doctor it should appear as: Dr. John Doe or John Doe, MD.
I would like to introduce you to Governor John Doe.
The address should read: Drs. John and Jane Doe or, Dr. John Doe and Dr. Jane Doe.
A baronet is addressed as "Sir", and his wife as "Lady". Exactly how to address the envelope is a little dicey , but "Sir John Doe and Lady Doe" would be acceptable, I would think.
Yes, you should include a comma after the name and before "PhD." For example, "John Doe, PhD," is the correct format.