He had to do boot camp , then Force Recon training, which would have taken at least 5 or 6 months. We stopped sending troops to Vietnam in 72, so the numbers don't add up.
Yes, they do. Someone 64 would have been born in 1954 or so, making them 16 in 1970, with a couple moths either way. They took 16 year olds in those days, with parental approval. I know because I have 3 friends who signed up, two went to Nam. Besides that, we had Marine embassy and consulate guards, as well as intel and advisors still serving there right up til the evacuation.