J.J.
OK, this may sound simplistic, but does he have a train set? My son was very close to that age when he started his "train phase" and is now 3 and it is still going strong. He will play trains for hours at a time! You can always take him to a friend's home that has one or even just a Barnes and Noble kids area to try it out and see if he has any interest. I don't know what I (or he) would do without it! I guess it is just a matter of finding that one special activity or toy that he loves. But yes, you are hitting prime tantrum time anyway. Be strong. It is just a phase. As for snacks, I do three meals a day and a small snack twice a day - if he asks, but my son rarely asks - because he is usually too busy in the play room with his precious trains - so I can't help you there.