V.C.
A few ideas . . .
If he's using a commode, the water 'splash' with #2 may bother him.
When he uses his pull-ups, have him wash his own bottom until it's clean and explain that it would be a lot easier to clean himself if he's used the potty and it's not squished all over his bottom.
Since he has a particular schedule to 'go', have him sit on the potty until he goes even if it's all night a time or two, and he'll get the message. Have a little reward for the first time he does use the potty, and set a goal of one week or whatever that if he uses it every time, he gets to go to McDonald's w/Dad or something that would be a treat for him.