Hi J.,
First let me encourage you! We are going through the same thing right now! My son is 3.5 and we have been trying since his third birthday.
Patience. From what I gather, boys have their own agenda as to when they are ready. I have come to realize that my son is a late-bloomer in this area and I am fine with that. The world is not going to stop and stare. Routines like what you are doing are good, but don't get too emotionally involved.Gentle persistance and patience will eventually pay off when he is really ready.
Cheerios in the toilet enthrall my son. Also when the weather is warmer I simply don't put diapers on him. He makes the decision at that point to go to the toilet. I am hoping that with our first bout of really warm weather that we can finish this up in a weekend!
Good work, but relax! :)