This is going to be long, but ok, in answer to your assertions:

Why did primates move about in groups having fewer males than females?
___ They don't. Primate groups are pretty much 50/50. If the ratio is skewed, it's because, like humans, males are more prone to getting themselves killed. http://pin.primate.wisc.edu/factsheets/entry/chimpanzee/behav

- Why males are fertile on each and every day of their adult lives but women are not?
___There is no species where males aren't fertile every day, and no species were females are. It has nothing to do with polygamy/monogamy but more population control.

- Why did most resourceful men in the past were known to be sexually promiscuous and had multiple wives? Why is this not the case with powerful women?

-Most powerful women had multiple lovers (Cleopatra, Queen Elizabeth 1st, Catherine the Great). But as I said before, being a monogamous species doesn't mean you lose sexual desire, just that it makes more sense for the continuation of the species. Other monogamous creatures, like swans, eagles, etc. All have sex outside of their partners.

- Why is prostitution the oldest trade in the world? Why do we still have more prostitutes and fewer gigolos? Is it not again a demand and supply scenario?

- No it's not. Women don't need to pay for sex. No matter how fat or ugly there will be a man who will have sex with her. Men can't say the same. In fact, this points more towards monogamy, because men will want to get a female to stay with them so they don't have to pay for sex.

- Why do men cheat on their wives even if they admit they love them? And why don’t women generally cheat on their husbands whom they love?
-Because monogamy doesn't mean you lose sexual desire.

- Why is a women’s body the focus of her sensual pleasures while for men it’s the women he is with?
Huh?

- Why most men would enjoy themselves having sex with any good looking women they meet but women would take time to accept a physical relationship.

-Now you're looking at social conditioning. There's much to say that women are just as happy to have random sex as men. However, it would probably have to do with women needing to be more selective when choosing the father of their children and their partner. Whereas men don't need to be as selective. This is more to do with the protector role of men, then monogamy or polygamy.

- Why women feel happy decking themselves up with cosmetics while men don’t? Is it not again appeasing your senses with your own charm and sexuality?

-to attract a mate. The most attractive woman will get the most attractive mate.

- Why magazines for women feature mainly clothes-line and fashion accessories while men’s magazines carry pictures of pretty female models on almost every page?

-Actually women's magazines talk mostly about how to get men.

- Why do men get bored sleeping with the same women and lose their interest sooner than the women get? And why do most men think, they would be able to perform better with a different and younger women?

-Now you're just making assumptions.