I wish I could help you on this one. I have three girls that all potty trained at 2. My son however, it was the day before his 4th birthday. I tryed everything. Looking back i wish I was more laid back about it and followed his lead more. Everyone told me he wouldn't do it until HE was ready. They were right.
He's not ready. When he cries and fights to get off the potty, what are you going to do? Force him to sit there? That will harm the process, not speed it up.
Wait until he is ready to sit there on his own.
And most toddlers like being naked. Taking off the clothes and the diaper is common and has nothing to do with potty training.