I was dating a guy last year who was 15 years younger than me, a guy I'd known professionally for three years - wait a minute - is your name Nick?
Sorry - but the similarities are freaky. My point is, had I received this letter, I would have positively swooned. Angela's right, the freakout potential will definitely be less with an *older woman*. (We have a great appreciation for sweet sincerity and generally speaking aren't looking for anyone to settle down and have babies with).
That said, I do encourage you to take some of Rose's edit suggestions to heart. It always takes fewer words to say everything in our hearts than we think it does.
Good luck sly guy!