I have a bunch of questions

[sunnydays]

Since he is able to remove the diaper himself, why not just tell him that if it is wet he can take it off and put it in a designated place and put his pants back on and go back to bed...by himself. If you are worried he will wet his pants, you could provide a pull-up for him to put on himself along with his pants. That takes the attention out of it, but also does not force him to sleep in a wet diaper if he truly did have an accident and needs a change.
I remember when my son went through a phase like this at bedtime...always saying he had to pee (I think he was 3 at the time as well). I ended up putting a potty in his room and told him that if he had to pee, he could pee in the potty and go back to bed. He never needed to use the potty, but it gave him no excuse to call me about this...put it into his own hands