[LostCause]

1.) Building a windshield wiper fairing won't do much as your wipers are probably in a stagnation region with little airflow anyways.

2.) Raking back the windshield doesn't seem to reduce drag as much as you'd expect, at least from what I've gathered. Raking does help, but it has diminishing returns beyond a certain point (I don't remember what that point is: it is a sharper angle than your's but much less than the new civic's). I guess what I'm trying to say is that a fairing will probably help, but not to the extent that a boattail/kammback would. Personally, I'd work on rounding the a-pillars (get rid of that rain gutter), streamline the frontend (Bumper/radiator) and add a partial kammback. Front wheel fairings, catamaraning the bottom, and ducting the radiator flow onto the hood are other untapped, incognito possibilities.

I would be very interested to see the results of your experiment, just don't forget that the best fruit isn't always at the top of the tree.

3.) Polycarbonate (Lexan) and Acrylic (Plexiglass) scratch extremely easily if not coated. Acrylic is much more transparent (optical grade is better than glass), but both would certainly suffice. Lexan has the added benefit of increased impact resistance. If you want to keep the fairing long term, be sure to get plastic with uv inhibitors, as both yellow in the sun.