As long as he knows that the diaper is going to catch whatever comes out, he really has no incentive to tell you he needs to go. There's really not much of a consequence if he pees in a diaper or poops in it. So, no more diaper. He needs to feel wet, needs to feel and smell poopy, frankly. He also is not too young, at three, to have to "help" you clean up the mess when he poops in his pants -- make him take them off, put them into a plastic bag, wipe his own bottom (as best he can, you will do the rest), wash and wash and wash his hands, even clean up the area where he was standing when it happened if anything's on the floor -- that all lets him know that if he poops and doesn't get to the potty, there is the simple fact that he must take time out of his play to clean up. Do not cave to pleas or crying -- and do not, do not scold or make it a punishment. It's just a fact: When you poop or pee in your pants you must clean up, so it's best if you get to the potty on time. That might help him tell you in advance better.
If that does not work, he is not ready enough for full-on training and probably wasn't ready to begin with. Some kids just do not train completely until well after three. Not what any parent likes to hear but it's true.
I, like the first person who posted, would not have associated potty training with food. I don't know how you go back on that now, unless you stop training for a while completely and reboot.
The fact he can pee every hour and is happy to do so might indicate he is holding back some urine most of the time -- he thinks peeing is a fun game and he gets treats too, so he might have learned (though not really consciously) that if he always can produce at least a little pee, he's going to get that treat each hour, and make mommy happy too. It's win-win in his mind but not good for his body or for real potty training. I DO believe in taking kids-in-training to the toilet regularly even if they do not ask, but taking him every hour may be too frequent and could be inadvertently teaching him to hold it in so he can be sure to "perform" and get his treat.
I might try first going cold turkey on diapers (training pants are the same thing to me - get him real underwear that he gets to pick out and won't want to see messy). If that plus the "stop everything to clean up" routine does not work, it might be time to halt altogether for a short period then restart but without treats as incentives. The incentive as he gets older needs to be the feeling he is clean and does not have to stop play in order to clean himself up.