Who believes that a man who couldn't type would use a very expensive typewriter to put together simple memos? Why would anyone do things like swap out typewheels to do a superscript in a simple memo?

Apply Occam's Razor:

On the one hand, we have a document that can be perfectly recreated in about 5 minutes using default settings on Microsoft Word.

On the other hand, using a very expensive typewriter and a lot of training, you can get fairly close to duplicating the memos with a lot of effort.

Which is the most likely explaination?

That doesn't even begin to address the other problems with the document, such as referring to a nonexistent manual (there was no AFM 35-13), ordering someone to do something "IAW" the manual (it isn't done), pressure supposedly being applied by a man who'd retired 18 months earlier, etc.

Seriously, if you still believe those memos are legit, then you're a dope.