You are lucky to have double pane windows, and unlucky at the same time. The flaky stuff is usually the solar film failing. You van use the 'Search' function and find folks who have broken, disassembled and used other methods to fix the ugly.
There can be a water line where the two end curved windows hold water when the gaskets siphon in rain - usually its bonded salts and etched, it can be reduced but not eliminated. More than a few windows have been shattered by folks trying to drill out a drain hole when there is standing water between the panes.
I had actually read some of the earlier posts about the film between the panes and I suppose that may be what it is, though it looks quite different from the photos. I'll post some photos on the weekend, but taking apart the windows looks like a huge job!