Well ability to reproduce is an important trait that organisms naturally have. And please list the species that organisms have non reproductive roles?
Ants, many bees and wasps, termites, some beetles, some snapping shrimp, some mole rats.
And no, saving sex till marriage is not a disorder, because it forms the natural family unit with both a mother and father to raise the children.
Fun facts: premarital celibacy is not necessary for marriage, marriage is not necessary for mother/father families, marriage does not guarantee families of any particular kinds. But nice of you to acknowledge you were wrong about non-reproductive behaviour being disordered.
And it is the second. I do not know how to sexually identify myself and masterbate outside of my fetish. And I do not watch porn videos as my Christian beliefs make me consider pornography immoral and exploitive of women. But in terms of looking up images, what would you consider to be varied?
Just go to any hentai site and look around, mate. No women were exploited for it and it's gonna cater to more tastes than you know exist.