Yes, they can still be addressed as Mr. President.
Yes a former US President can run for office of Vice President of the United States. A former US President can run and be elected for any other type of office.
The correct title for a former president of the United States is "former President."
Former US President Ronald Reagan
Ronald Reagan
No former US president died in 1970. Closest was Dwight Eisenhower who died Mar 28, 1969.
I address letter to former state representative as US representative.
Gerald ford
Martin Van Buren was the 8th US President.
Washington
yes
Mr. President
George H.W. Bush is the oldest living former US president. He is 86 years old.