Can you clarify where you are at. You say you have 0 impressions, but also that you have traffic. That seems contradictory.

If it is 0 - as in absolute flatline the first think I would check is your tracking code.  If you have server stats as well maybe check one against the other to make sure that you don't just have a tracking error.  However your pages are indexed and you have google analytics tracking code in place, so a total flat line in traffic seems unlikely.

Check your top entry sources from before the drop. What were your top terms - what pages were they panding on. Are you still ranking for those terms? Has the URL changed (in which case maybe redirect from the old one), if not how do the new and old pages compare.

I've often seen an initial conversion drop when sites are changed around - even when the changes are big improvements.  On sites where you have a lot of repeat visitors this can be because people are used to the site as it was.

I'd honestly start with the assumption that you are building a new site, rather than changing the platform from the existing one.  If you think that the current content is strong then keep that, but start afresh with the actual build.

Flash professional does allow you to export flash content as HTML. If you have flash professional CS6+ and the original source files you can do this.  There is a demo of how here: http://tv.adobe.com/watch/cs6-creative-cloud-feature-tour-for-web/exporting-flash-content-as-html-in-flash-professional-cs6/

Whether you would want to use the resulting HTML as your website is debatable. I wouldn't. I'd rather pay someone to rebuild a simple version of the site from scratch and at least know that the structure and on page set-up is all good.

What is the aim of switching? Flash websites are not great for most purposes, however neither are badly made HTML ones. If your aim is SEO success then I doubt that exporting from flash will help you much.

If people are posting questions about glazing there is definitely an opportunity here.  You could start blogging great answers to common questions so and then set up alerts for when those questions appear.  When they do you can post a short answer to the question but provide a link to the indepth version.

This also means you start improving the quality / depth of content on your site at the same time, which has to be a good thing.

Cyril - I honestly wouldn't worry about this. The vast majority of sites with https behave like this and it doesn't cause a problem.  Your canonical is extra protection against it.