Hi,
I only have a girl, but take care of friends/family members boy's, so I know a little about both when it comes to potty training. First off, in my opinion boys generally train later than girls. Second off, there is no right time according to age when to do it, its when they are ready. Looking for clues, can they hold it for long periods of time, can they communicate they need to use potty. For myself, I tried w/my daughter at 2, no luck. At 2.5, not much better. At about 1 month before she turned 3 I tried and it worked. I probably would've trained her sometime in her 3's, but had to put her in a preschool where the kids had to be trained asap.
I read this in a parenting books, insturucting to ONLY change diaper in bathroom. When they poop, have them watch you empty diaper into toilet. Then you make them sit on the potty all of the time, trying to do it every hr, (or when you think they will need to go). My friend swears by taking the potty training kid to pick out their fav character underwear, but my daughter wasn't too impressed with this. I used candy to reward my daughter,but you mentioned this didnt work. Pick something he really likes, even if its a toy, etc.
ALSO, DO NOT use diapers or pull ups (only pull ups that have cool alert or cloth-best choice). This is HUGE, they don't like to be cold and wet, so this reinforces potty. A couple of other tips include, a watch my friend got online, called the potty training watch. It has a little song that goes off every 30 mins (or whatever you set it to), she swears by it. Another friend would only let boy watch tv, if he was sitting,(trying), to go on the potty. Also, I've heard of moms using cherrios to have boys "aim" at in the potty. My mother in law says it was so easy to train my husband and his 3 brothers b/c they lived on a ranch and they learned by peeing outside, (I know its a little country, but it worked!)
MOST importantly though is not to worry about it, b/c they WILL train when they are ready. I can remember so clearly thinking how many others were trained before my kid and that mine would be wearing pull ups in elementary, (my daughter is very stubborn too!). I have babysat a couple of poop smearers, you are not alone!!!! Good luck and don't worry!!!