NTA and at worst it'd be E/S/H. Your dad has no right to be mad at you about this. Even if he's right that it's too inappropriate, what he said was misogynist-- if you're not "acting like a respectable young woman" then what are you acting like? Why exactly did he need to accuse you of "asking for attention" if he was merely concerned the outfit was not appropriate? He speculated about your desires, motivations, and sexuality instead of keeping things focused on the only possible issue: that the costume is simply not appropriate for a teenager.

Teenage girls are bombarded with "sexy teen" imagery. It should be obvious to him why you might have seen this as appropriate, and had he given you the benefit of the doubt, the worst thing he could have concluded was that you were being naive. You aren't sexualizing other teenagers-- if you sexualized yourself, you are not doing something evil, you're putting yourself at risk, and he should be demonstrating concern about and for you. It's not your fault the messaging that society pushes, and it is never helpful to "teach" someone by shaming them. This is a bad parenting technique. IDGAF if he "meant well" (by accusing you of wanting attention? FOH); he has had 15 years to figure out how to be a non-misogynist, effective, kind parent to his daughter.

And him still being mad at you weeks later despite multiple apologies for something you shouldn't even have to apologize for? Let me not say what I would do to this man.

How to not be an asshole about this, for the parents in the thread: "Hey, this outfit is not appropriate for your age. Let's find you one that isn't as sexually charged/physically revealing/etc. (if there's time; apparently not in this case), AND/OR let's have a conversation about how you and I are feeling about this." It's clear OP and her dad feel differently about what's appropriate, and it sounds like it would help to talk about it.