I agree on some points of the OP.
However : (and puhuleeease, leave religeon out of the discussion, because that is one of the points I agree with the OP : this has nothing to do with religeon, but all with science and facts)...

Well, here's my question, if life (basic life) cannot start to exist out of the blue and if there's always an external intervention necessary, where is the one who intervenes coming from??

I do seriously consider in believing external intervention when it comes to the "human" race at some point in history : meaning at a certain point in history there was nothing which can be called "culture" or "knowledge". We were not that much different from primates.
However, at a given moment, primates became smarter and (just to make a long story short and not to complicate things) started to develop unseen capabilities on this planet (from which the most important the capability to change the environment such way to fit the needs, instead of moving elsewhere to an environment which fits the needs already, as basically, this is what being human is all about : control).
But the theory I believe in, also states that the potential was already here (meaning : life was here and it just started to exist, and finally a couple of tens of thousands years ago, a species evolved which had the correct "specification" in order to become what we are now (meaning : body structure, volume of the skull, specific kind of tongue, hands with a thumb, possibility to walk on 2 legs instead of 4 etc... etc...) And then, due to intervention (aliens, timetravellers, whatever), evolution leaped forward, probably due to DNA engineering (which is perfectly possible when those intervening had a knowledge of DNA which is about 3 or 4 decades more advanced than our current knowledge).

So : intervention : yes. But for me this does not exclude the possibility that life itself can start to exist out of the blue if the right conditions are there. I think that somewhere in the Universe, there are a couple of very, very ancient races which had to evolve during thousands of milennia. And maybe, they just give a push to intelligent life on places in the universe where they think it might work and evolve into more intelligent life later on.