My Grandpa always says you're only as old as you act. He's 84 but looks and acts like he's 60. His second wife was 12 years older than him. They had a great marriage. Had one fight in the 40 years they were together.
As far as the missionary, don't sweat it. I had a crush on one of the sisters serving in my ward here. (I can't stand the Singles Wards here in Florida. College Park ward especially...)
But anyways, I knew she liked me as well. Happens. We kept things appropriate, never alone g together, ect. A *little* flirting. But, after I met my Gf/Fiance Sarah, The sister was gone from my mind. It was funny to watch them meeting each other. Never seen a missionary give such a dirty look.