R.H.
It seems to me your doing great just keep up what your doing. The only thing i don't agree with is object rewards kids loves getting phrase there is no need for toys or food rewards. Have you ever noticed how happy kids get when you hug and tell them how good of a job they did. At the most i use a chart with stars.
If he holds his poop tell him the truth. If you have to go poop and you don't let your self it will make your tummy hurt, you can get sick from it and next time you go poop it will prob. hurt. Children understand getting sick and tummies hurting and going to the bathroom hurting and don't want any of them. They will do what they can to prevent it...lol