L.R.
Do a search here on Mamapedia for other potty training posts, especially those for three-year-old boys. They're there. You will find a lot of advice already on here....
Putting him back into the pull-ups unfortunately sent him the message that he could pee in them, so you may have to redo the potty training for pee as well as tackle it for poop. But yes, he sounds like he's not ready and doesn't have the interest or the body control. You could just wait a little longer and start from scratch in a while.
Be sure to rule out things like a fear of pooping - some kids don't understand that poop is waste; they see it as "part of themselves" that they are somehow losing down a mysterious, dark hole called the toilet. If that's not an issue he's expressing, he may just be too immature yet.
When the time comes, a reward system can be great but only IF he is mature enough to connect his actions with getting the reward; if you try this, make it doable and achievable -- don't say "you have to do a week of no accidents to get reward X," because that is eternity to him; instead make it one day, then two, etc. as he improves.
But anyway -- search on Mamapedia for tons on this topic.