That is one crappy seduction attempt. And why would anyone leave evidence of attempted seduction in a place that is likely to be seen by her peers and very probably family members? And I think you got the date wrong. The yearbook was signed in 1977.
I don’t know what you mean by sharpened his approach.
To your point, it probably is a crappy attempt at overt sentimentality. After all, Moore was a straight-arrow MP in Vietnam until 1974, so what did he know? 1977 was his first year of dating, so he sounds like a nervous teen. He built up his dating confidence by 1980.
I'm not saying this is what happened, but I am trying to come up with plausible scenarios that rely on the fewest assumptions.
-PJ