Roblin, this is a beautiful essay and I have tears in my eyes. It seems we are living parallel lives as I can relate to everything you've written here. You sound like an amazing father and your son will appreciate you more and more as time goes on.
My son and daughter both left home a couple of years ago, to university and then work. We miss them and have nostalgic moments every day. However, life moves along and we enjoy each other's company in different ways now.
Your story brought back memories that made my heart squeeze. Keep writing.