I just want to offer my encouragement to all the moms of 3+ boys who are struggling with PTing. It can be done and my son is here to prove it! (I hope I am not jinxing myself or him by celebrating here!!!)
My son turned 3 in November, had absolutely no interest in PT, wore pull ups for about 2 months with no progress, and then -- last Saturday he declared he wanted to wear undies. So that was that and he's been in them since. He is still working on making poops in the potty, but hallelujeh, he's been using the potty for peeps since Saturday. He is even initiating it himself. I am not taking him all the time.
So, yes, it was like a switch flipped in his brain. He wanted to do it and he did. So your son can, too! I promise!!!
And thank you to all those who have given advice here. It helped me A LOT