I must admit that the whole midi-chlorian issue does leave a somewhat bitter taste in my mouth. In my very humble opinion it does diminish the spiritual nature of the Jedi knowing that a great Jedi may be judged on the sum of their midi-chlorians. On the other hand, the scientific rationale does lend some 'reality' (and I use the term loosely) to the nature of the Force. Whether or not it was necessary for Mr Lucas to even raise the issue of these midi-chlorians is another interesting debate.
Regarding Anakin Skywalker, the catalyst for his creation may have been Darth Plagueis, Darth Sidious or even the Force itself (not that this would mean the Force is sentient, but the 'vergence' Qui Gon speaks of may be a naturally occurring phenomena of the Force). Whatever the cause, we know that Anakin was created by the Force.
I do not think that we can disagree over the existence of midi-chlorians. The films clearly state that these organisms exist and briefly describe their relationship with the force. Denying their existence in the Star Wars universe would be like denying the existence of lightsabres.
That is a good point about whether or not Kreia would have knowledge of midi-chlorians. An argument could be made that she would considering the relative similarities between the technology of the movies and the KOTOR series. Although their is a vast time difference between the setting of the two, technology has not evolved (at least on the surface) that much. Artificial intelligence seems to exist, lightsabres operate on the same principles, space flight seems the same, and blasters operate on the same dynamics. One could therefore argue that medical science would be developed enough to discover the existence of midi-chlorians. This is of course all conjecture.