Hair is not about attraction, it's that an uncovered head (for men as well, men wear a kippah) is considered uncouth, and it's a way to disrespect someone. Think about hat wearing in the US 100 years ago - no one respectful would be caught outdoors without a hat.

There is no rule about mixed fibers. Instead there is a rule about combining wool + linen, and the reason is simple enough: It was reserved for ceremonial use, and not permitted for mundane use.

Specifically the priestly garments were made of it, and Tzitzit (which are worn by all Jewish men, not just priests) are made of it.

Milk and meat are separated because it's considered "rude" (wish I had a better word, maybe "boorish") to put the meat of a dead animal in the same liquid that it makes to feed its young. It's also not permitted to kill a parent animal and its child in the same day, for the same reason.