I have been trying to get my pages out of the Supplemental results listing without success.

At this point I believe it is better to start with a fresh domain, because once Google labeled you as a "low quality" writer, it is useless to get new links, to make static pages instead of dynamic, clean the site from links to bad neighborhoods or all the other recipies.

Anyone agrees on this drastic strategy? Any other solution?

Time.

Google doesn't crawl pages in it's supplemental index very often, so most likely it hasn't seen your changes yet. More inbound links ( from quality, often updated pages ) might help fix that; most people get into the Google index not by applying, but by having links.

On the other hand, you might be right about Google sticking to their first impression ... that's only natural in humans, so I wouldn't be shocked to learn a company run by humans does the same thing, using algorithms written by humans.