OK, I think you need to see that you are getting way too worked up about this. I know it is frustrating but I am learning that my 4 year old DD feeds off my emotions and the more worked up I get about something, the more apt she is to "lose it." It also sounds like you are engaging in a battle of the wills and determined to win so you are the boss and you need to ask yourself is it really worth it. When he starts seeing you as angry mommy, trying to win your approval but can't help how he feels about the clothes, when he ends up going to school/day care all upset. Believe me, I've been there too, so I am not trying to make you feel bad - just that I've begun to look at the situation and realize that...it's just clothes. To me anyway. To DD, it's a whole lot more - it's her identity, her wanting to choose what she wants, and being able to make her own decisions (she's never been good about the whole "2 choices" thing anyway). It's not a hill worth dying on, IMO.
Sounds to me though like he might have some sensory issues, or a sensory processing disorder, which can make them more sensitive to certain fabrics, how things feel, etc. I would Google it to get more information, and I would also talk to his pediatrician about the possibility. I would also try to just figure what clothes are his favorite, wash them as needed and have them available as much as possible - washing a small load every few days has got to be less aggravation than what you are going through right now. Get rid of the items that he just cannot stand - because making him wear them isn't really teaching him anything, now is it?
ETA: Just wanted to add that DD does not seem to have sensory issues -she is just strong-willed and opinionated and I've learned that things can quickly escalate into a power struggle, and sometimes it's just not worth it. She went to day care today wearing a dress that was given to us as a gift, a dress I don't care for because it's an almost all-white sundress and it reminds me of a nightgown. But that is what she wanted and there was no changing her mind, so I just remembered that again, it's not worth the struggle, the tears, etc. - it's just one dress for one day and she will wear something different tomorrow. She does understand that some things will just not be allowed because of weather and/or because they are dirty. If she is insistent on sometimes wearing something that is not appropriate for the weather and time of year, those items get put away in another closet - if she doesn't see them, it doesn't bother her as much when I have to say no and she has to put them back. When she starts kindergarten in Sept., her school requires uniforms, so I figure that's going to solve many of the battles right there!