Probably a dead post, but I'd agree with Mendo view. Using a new razor blade to clean stickers, paint, silicone etc is very common practice and should not damage or scratch the glass if care is used... I can't comment on the "rough side of the glass" statements, but some caution should be exercised in the even that there is a coating of low e on the interior surface that could be more prone to scratching. That may be what happened here...

+1 Gotta see the application. I am going to guess "no" with some creative install options but a picture of the interior and exterior would put the question to bed.

What a delightful view! You don't show how high your ceiling is or what configuration it follows above your window wall, but if it is not vaulted you might consider ceiling-mounted tracks that will allow drapes to be opened and closed across the full sweep of the windows. Ceiling-mounted curtain suspension systems are easiest to find for stages, studios, and hospitals, but this type of suspension system is also manufactured for home use. The downside is that you lose the decorative element that wall-mounted rods and supports can provide. See http://www.curtain-tracks.com/hardware/ceiling-mounted/ or http://draperytracksystems.com/news/ Here is a link that might be useful: Fitting A Ceiling Mounted Curtain Track

When you say 'black windows' what exactly do you mean? The entire frame or just the trim piece? I would be concerned that black windows will just fade into your mansard roof like your front door fades into the background now. I like what you have now,