A man's virginity is not equal to a woman's.

That's a type of sin against nature.

St. Thomas gives this ranking (II II q. 154 a. 12 ad 4), in ascending gravity.
I think he means this ranking:
1. "uncleanness, which consists in the mere omission of copulation with another"
2. "sodomy, because use of the right sex is not observed"
3. "not observing the right manner of copulation, which is more grievous if the abuse regards the "vas" than if it affects the manner of copulation in respect of other circuмstances"
4. "bestiality, because use of the due species is not observed"

 A man's virginity is nothing

There are plenty of virgin men who won't make good husbands as they can't provide for a family. I'm saying a man's virginity has little to do with his ability to be a good father and husband.

On the other hand a woman's virginity is extremely valuable and important. It directly correlates with the chance of divorce and adultery. It determines whether the offspring is tainted by other mans DNA (previous partners), it also greatly effects the woman's psychology, expectations, pleasure and satisfaction. It also undermines the husband's greatly as well as his authority. He is the head of the house, yet his wife gave herself/was taken by another man, for less than marriage. What an absolute dishonor, an extreme disrespect. A man being second to another man to his own wife.

Goodness gracious me! Some of you people seem to be unable to fathom the differences in men and woman! A man's virginity is nothing, he doesn't even have a hymen. But a woman being a virgin has always been a necessity throughout history. The two are incomparable. While it's certainly not ideal for the man to not be a virgin, for a woman, a lack of virginity is a deal breaker.

Really think about why rapists would get the death penalty (wasted/ruined a woman) and fornicators were forced into marriage (because who would marry this non-virgin woman?).

I agree with all of this.
Nevertheless, I don't want men to think that using porn is nothing. Having a history of porn use affects the man psychologically. Not to mention that porn use goes along with self abuse, and that does affect a man's ability to render the marital debt to his wife later. A man really is damaged goods, depending on how long and what kind of porn he used. I've heard horror stories of men being impotent while "being with" a 10 (a "dime", a supermodel) due to past porn use. He can't perform with a real woman.
Maybe porn use is worse, for a man, than having a single human female partner.
-a man

Where does self-abuse fall here?

Those are not the same thing.

the sin of "uncleanness" (immunditiæ) which some call "effeminacy" (mollitiem [lit. "softness"]).