"So why does a sensually stimulating activity that often results in true feelings of happiness generate so much conflict?" I think this question is an altogether different one. At its core, sex is primarily about reproduction, and mates can be scarce resources, hence the competition and conflict. But it's still no controversy.

"Why would God want to deprive us of this happiness if he loves us?" First we need to establish that there is a God. Until then all we can say that people are told in God's name to do something. And some people seem to get the kick out of trying to portray a natural behavior as anything other than natural.

I would argue that extra-marital sex became forbidden in order to ensure the paternity of the children. That is why sex is a more serious offense for women than for men. Males try to ensure that they are investing in the raising of their own biological offspring, and one of the easiest ways is to fend off rivals and enforce monogamy on the females.

The controversy is the difference between what people feel as a natural desire and the dogmatic prohibition of sex.

If, for example, you would say "don't kill, because god say so", than the morality part of this is the "don't kill", the religion part is "because god says so". In this sense morality is the code of conduct, religion is a justification. Changing or removing the justification doesn't change the code of conduct.

1. "Should be" as in "should any text be written in order to be relevant for a long time?".

This puts the emphasis on the writer of the text to make it so that the text answers questions in the far future. Imagine the scribe writing the Old Testament on the parchment and thinking about how to answer questions about DNA or the nuclear fusion. I think we know the answer to this, we don't need to look further the endorsment of slavery in the Bible did not stand the test of reason.

2. "Should be" as in "should we today consider it relevant?". 

Insofar as the issues addressed in the text and the answers given are relevant to the current times, and not further. The relevancy is not decided by our wishful thinking but by the text's relationship to the current issues. So it either de facto is relevant, or it isn't. But there is no necessity that it should be. That would mean putting outdated issues or outdated answers on life support.

I couldn't read your whole idea - it is way too long. I would suggest breaking it up into smaller
ideas and post them separatelly.

What you wrote about evolution caught my eyes and thought to respond to that.

Evolution as far as I know is a process driven by "the non-random survival of random mutations". That means that the mutations are random, but only the ones that prove to be beneficial will survive. Beneficial = gives the posessor of the mutation better chances of surviving and creating offspring than the specimens without the mutation. A antelop running faster than the rest will more likely to survive than the slower antelopes because the lion catches the slower ones.

If you would like to see a beneficial mutation, you might want to check the recent research done on the finches of the Galapagos. It shows that the size of their beak changes depending the type and scarcity of the available food.

As for the development of the insects' wings, you might want to read Richard Dawkins' 'Climbing Mount Improbable'. He discusses just this issue in chapter 4 ' Getting off the Ground'. The research described there gives a scientific explanation, along with evidence supporting it.

Also, evolution has no end goal.

Until proven so, it is just an assumption that it (or any other "holy scripture") is the word of any deity. Assumptions are not reasons.