[Havoc]

2. Religion, as well as it's sketchy origins, just seems to have been a primitive theory for existence, how the world works etc. Now we have discovered more detailed, scientific theories.

Tsss... Don't you know that the church updates the bible whenever a big undeniable discovery is made? That or they come up with some way to find it back in the bible.

3. If religion is the truth, how come there are so many different religions then?

Because the story of god works the same as any other fairy tale: It's told differently everywhere you go. The one thing all religions except for China have in common is that there is 1 god and 1 prophet. For example these were God/Jezus for christianity and Allah/Mohammed for Islam. Furthermore there are a lot of stories in the Bible and the Kur'an that are virtually the same with some details changed.
My theory on what happened thousands of years ago is that some guy came up with a cool story about how the world was created. He told his story to his family, his friends and they told it to their family and friends. Remember there was no internet or book stores back then, any story worth telling would be told for years on end to thousands of people.
Through the course of salesmen traveling all over the world to sell their stuff the stories were spread worldwide but not in the exact same form. Since cultures were different on different ends of the world, the story was bit by bit altered to fit the culture it was being introduced to, whichever one that is. Now we have two versions of practically the same story floating around and people a few thousand years later to stupid to realize it. Gotta love humanity.