Judging from the content of this thread so far, two things come to mind. One is that is all but impossible to acquire a native-like phonetic ability after starting a foreign language at an adult age. What is certainly possible with a lot of hard work is the attenuation of a foreign accent to the point where it is not noticeable. But that is not the same as acquiring native-like pronunciation.
My other observation is that there is fundamentally only one way to acquire a good accent: extensive active meaningful interaction with native speakers starting at the earliest age possible.
I think there is something to be said for the idea of a neurological window for the acquisition of accent in the 0 - 14 year zone. This, by the say, is the basic idea of French immersion education here in Canada. French immersion in an English-speaking environment has its limitations of course and does not produce perfectly bilingual graduates. But it does expose the children to French at an ideal age and does create a foundation that may be useful at a later stage. Now that French immersion has been around long enough, we can now see the results in graduates who have a much better, albeit very far from native-like, grasp of French.
As others have pointed out here, learning a language, especially pronunciation, is basically a lot of imitation, repetition and correction in the right environment. This often means some combination of four things: live, love, work and study in the target language. It's not more complicated than that, but it's usually more easier said than done.
Thank you for your recording. Awesome.