Well, from the viewpoint of someone who thinks God would bless a marriage of you and your 19 year old friend, assuming you were a fit match for each other, you have had a non-sexual relationship for a long time and he has had plenty of chance to tip you if he feels more than a friend/son/nephew type attraction to you. There is probably no point in disturbing your good relationship with a very belatedly announced attraction on your side. But just in case he's so polite that you seriously think he might be in love with you but afraid to show it, and you are willing to take a small risk to investigate that, you could leave out a discussion starter like the book "Loving Someone Gay" (a sort of manual for parents and friends on how to handle it when someone they know comes out as gay).

Also, pray about the matter, because if he listens to the holy spirit and he loves you in a sexual way, the lord will find some way to bring you together. My own bf is a christian but not visibly practicing... but the speed of his response to prayers I make -- that he doesn't know about -- never fails to awe me.

It seems very unlikely, so on the practical side, don't let the tension build up by failing to masturbate a lot. Having a high level of sexual tension gets to be a lot like being drunk when there's someone around who you're very much smitten with, and you may find yourself doing things you don't really want to. Quell yourself, but it's just as well not to do it with porn because he might see something if you're careless -- and everyone is a little careless at times.