I would definitely recommend doing full height drapery here- even if they are stationary panels (less fabric and less costly). Most likely they would need to be custom, but shop around for small scale local seamstresses- often they are your best value. Also, keep in mind the fabric will be the most costly part so shopping around for that will make a big difference as well. You may also want to consider blinds on the windows depending on where the light comes through at different times of day and how much privacy you require.

As for the cable under the stairs, that is an awkward location. If you would like to move the cable without demolishing anything, I would suggest installing white raceway channeling just above your baseboards. This can be purchased at most hardware stores. See link below for more information on this.

http://www.diynetwork.com/how-to/how-to-hide-wiring-behind-baseboard-or-installing-a-raceway/page-2.html

yep, custom, and be sure to use at least two widths of fabric per side so they don't look too skimpy. --minimum of 20 yards of fabric needed.

You could use solar shades under the stationary drapes for brightness but glare control.