Nice grid. A couple more crossovers would up the challenge

A “score” isn’t really a unit of time — it just means 20 of something. Just like a “dozen” isn’t a unit of donuts. When Lincoln said “four score and seven years,” he just meant [(4x20)+7] years.

I really loved this grid, except "score" let it down. Score isn't a unit of time, it just means twenty-ish. In the Gettysburg Address, Lincoln says "Four score and seven years ago", that doesn't mean (4 x score) + (7 x years), it means (4 x score + 7) x years. That is, "four score and seven" is just a fancy way of saying 87.