D.B.
I had 4 girls who all trained by 1 year, I had 2 boys that was much more difficult. If I was near you, I would ask several questions to give the best advice. Have you tried reinforcement yet? Stickers, bragging etc? Do you have a small potty for him to use? You could put a target with marker in the bottom to help his aim. Or put some cherros in the stool to use to aim. Make it non-stressful and fun. If he don't want to get a diaper changed and it is possible, leave it on him. Just don't make a big deal out of things that upset you. He may want the attention. If someone else can help you with this it would be helpful.