"I swear by God to be faithful to you" sounds completely different from saying: "I promise that I will not break my commitment."

That's just it though: it doesn't sound completely different. Also, Holy Matrimony isn't different than two people (of either sex, gender, or sexuality) agreeing to live monogamously together. For it to sound completely different in my ears, God would have to be real to my mind. But He, or She, or It isn't, so it sounds the same as "May the wrath of Gandalf descend upon me if I break this promise!" See how that works? I really have no problem with it sounding completely different to you though, you're welcome to your beliefs, I mean that.

Now, if you say that Christians themselves behaved cruel and violent, this would be true. It nevertheless makes the ideal not to be cruel and brutal not obsolete, though. It underpins it.

That's right. So, wouldn't you say then that it doesn't really make a difference if belief in God exists or not? And couldn't the exact same be said about any idealism? I'm sure humanists could, and would, behave cruelly and violently given certain circumstances, but that nevertheless wouldn't make the humanist ideals obsolete. Also, I'm sure Nazis could, and would, behave perfectly loving and caring, but that wouldn't make their ideals right.

I'll come back to what we seemed to agree on at the beginning. That the interpretation of what the religious scriptures have left us allows for intimate contemplation and interpretation.

I agreed to that with a rather important footnote, namely that the same can be said about many books and epics. I found it refreshing to see someone regarding the Bible in this light because it's something your average Christian wouldn't agree with. The Bible is supposed to be the absolute true word of God, and the (one and only) right interpretation thereof is left in the hands of the many different religious authorities and denominations. Your interpretation of the first part of Genesis was, and still is, especially refreshing to me.

Why do you think that films like Lord of the Rings or Game of Thrones move us if those involved in the story didn't really believe in the oath they had taken?

I still haven't seen Game of Thrones, nor have I read A Song of Ice and Fire, but The Lord of the Rings makes my point much more than yours. The oaths in that story come from interpersonal relationships and promises; rarely do we see such a strong commitment between two individuals as between Sam and Frodo and, the glue that holds the Fellowship together also is the glue of a friendship forged through shared struggles and promises made to each other. It's the becoming and the testing of that friendship that moves us all, religious and non-religious people alike because we can all deeply relate to that.

Because I believe in God doesn't mean I've stopped wondering...

And I never said you did stop wondering. I'm saying that William Lane Craig, who has a huge following, places God in the few remaining gaps in plausible explanations of the material world provided by an honest and rigorous scientific examination of that material world. I'm saying that in my mind, it's as useless to try to prove the existence of God, as it is to try to prove the existence of Gandalf or Sauron. That's my opinion as well as the opinion of all the scientists I've heard on the subject. That is because a God, by its very nature, is supernatural and science only deals with the natural world.

It's perfectly fine to have personal faith, as that entails so much more than just the question if a God exists or not. But faith is still faith and science is still science. Science is the art of not knowing. It doesn't deal with certainties, only probabilities, as in "it's more probable that God doesn't exist" and "it's more probable than not that our universe had a beginning". But the universe could be eternal. We just don't know.