For those who are still confused: nowhere is it said that midichlorians create the force (at least no more than any other living thing.) They're merely a conduit through which the force can communicate and since midichlorians exist in the cells of all living things, that conduit is always there for everyone, whether they listen to it or not.
All having a high midichlorian count means is that a person is naturally gifted in begin able to more easily feel and wield the force. That's it.
For the average person, it's certainly *much* more difficult to do what Jedi do but not impossible given enough time, willingness and dedicated training.
If instead of living a life of moisture farming and irascible grumpiness, Owen Lars had spent his entire life training and meditating atop a lonely mountain hermitage, he'd also be able to feel the force, gain insights and maybe even perform the odd physics defying feat of wizardry--Indeed, this is probably how the Jedi first got started--Luke on the other hand apparently managed to pick it up in a long weekend of hands-on instruction, because he's naturally gifted.
It's no different than any other kind of gift really and it can only take you so far. If a person born with an innate aptitude for music never bothered to practice, then they'd make a lousy musician compared to the person who worked and struggled and practised at it their whole lives to be as good as they can possibly be.
Maybe. Pretty sure though that it's intentionally vague whether it is or is not the Force working in that scene. (My own opinion: He was damn lucky. For a minute.)
The vagueness was kind of the point since for people like Baze and Chirrut who are not as naturally gifted in feeling the force as Jedi (yes, because midichlorians), it has to be an act of faith. Chirrut didn't *know* the force was with him, but he *believed* it and that faith was rewarded.