mur11, not bad, but there are a few things I'd want to quibble with in that summary.
First the idea that it's "predominately male" or that there is a "weaker sex". I think the opposite. Women have just as much an incentive to cheat as men do. It's in a woman's interest to mate with the strongest/healthiest available males, but have her children raised by the most successful/wealthiest. In addition both men and women have a genetic advantage in mating with multiple partners--greater diversity and gene mixing--so even if you're only going to have 2 or 3 kids, it makes sense not to have them with the same person. Moreover in any relationship the concept is that one partner may have the upper hand, in terms of being relatively more attractive, enabling them to extract more concessions in the relationship, and also more likely to have alternate sexual opportunities. That partner is as likely to be female as male.
Second I wouldn't say that monogamy is "falsely considered to be normal behavior", I think the whole range of sexual activity is normal behavior. Plainly there are significant organizational advantages in monogamous relationships, which is why they are the default mode--cheating, after all, is only well defined relative to monogamy. People will choose a relationship mode that maximizes their opportunities. I find it very rewarding to have a wife or girlfriend, even as I cheat on her. Also people with few realistic opportunities for adultery are likely to value monogamy, as are people who are in relationships where they're unable to extract the concessions necessary to commit it. That's a normal, realistic, pragmatic choice based on the capabilities and expectations that individual has about their opportunities. Others with more ability to attract multiple partners and to extract concessions are going to engage in adultery. Both choices are normal, and depend on the individuals attractiveness, situation, and abilities. It is still "life denying" to choose monogamy in those cases, but since the individual has not really got the opportunities to live a fully self actualized life, choosing monogamy, and some measure of self-denial, is in fact a sensible and therefore normal choice for that person.
I also don't know if you can really say that morality can be codified for "all other human interactions", but it certainly seems possible for most of them. The other example that comes to mind where codified morality is notoriously difficult is war, hence not coincidentally that famous aphorism, "all is fair in love and war". Well, not ALL is fair--in both cases we disapprove of aggressive violence--but many of the ordinary rules we live by elsewhere break down both in the case of sexual relationships, and in the case of military confrontation. In both cases you have individuals striving in an existential competition--the winner reproduces, the loser does not, and participants bring all capabilities, skills, and abilities to bear in an endlessly complex and frequently surprising way. Both activities also rely heavily on deception and appearances, so just as you can say "truth is the first casualty of war", it's probably just as accurate to say that "truth is the first casualty of love".
I don't agree with this: "Love, commitment, and honesty in the name of love and commitment are all artificial constructs practiced by the sexually weak or life-denying people." Love, commitment, honesty are not artificial constructs, they are real, fulfilling, and important aspects of being human, but love in particular exists within a spectacularly complex space that tends to defy rational analysis. In both love and war you will find people doing apparently irrational things that, if you were fully in their shoes actually makes perfect sense, but only in full context using deep knowledge of the relationship, including much of that is simply raw human intuition, empathy, emotional/social intelligence, and cannily accurate hunches rather than formal logical analysis. Literally in both love and war people grapple with "I think that he thinks that I think that he thinks that I will do X next, therefore I'm doing Y." Stuff like that depends far more on intuition and emotional intelligence than on any ability to apply rational thought--it's just too complex, with too many unknowns and too much uncertainty. Yet people are good at it.
Finally I think it's worth highlighting that there are some outright assumptions there, things that you could disagree with. The main one is the "life affirming" assumption, which essentially defines "good" in terms of our own humanity and thus something that is fundamental to who we are at least cannot be bad. That's an outright assumption. It is possible to make the "life denying" assumption, and many people do. The life denying assumption is that there is some more perfect ideal, handed down from somewhere (God?), independent of our existence, and compared to which we are inferior and bad. Thus there are moralities with concepts like "original sin", or the Buddhist notion that the entire world is some false illusion to be transcended. Plainly the "life denying" assumption is an equally valid assumption and many people live by it. It's a choice, one I've made, and not a conclusive argument. I just agree to disagree with those who think humanity is inherently evil/bad/wrong.
I agree with much of the rest of what you wrote, at least in general you have the gist correct, with a few quibbles like that.