Here's an example of a letter from 1972 evidently done on the same kind of typewriter:
http://www.genetunney.com/letter8.html
This font thing may not have legs.
The 1972 letter you posted looks real. The ANG docs do not. The question is not whether Times New Roman was available in 1972, the question is whether Times New Roman was available with superscript and smart quotes in 1972. The answer is no.
Also, look at the size of the font in the 1972 letter you posted. Much larger, as would be expected.
You may be able to explain away one discrepancy at a time, but remember folks, its the totality of them that counts.
It's already been established that typewriters with proportional typefaces were available in the early 1970s.
Incidentally, the Tunney letter is clearly not written in the same typeface as the alleged memos: the "legs" of the "M" appear to slant outwards, the downstroke of the "7" is curved, the downstroke of the "9" reaches below the line, and the "P" and "B" appear to be wider.