Yes, this is correct .
1 battery - 1 hour to -1:20 of recording.
If your interview is 1 hour long then remember there is a recording limit of 30 min. per record.
Good discussion! I usually have both approaches: starting create edits, then looking for music and then selected music inspiring further edits or sometimes is even change all the video idea. :-)
My choice for music is http://tiny.cc/Royalty_Free_Music and latest video with using royalty free tracks is:
"Las Vegas - Night Strip Walk" http://www.youtube.com/watch?v=1Y4R3A0nrh0
(btw here I spent just $62 for all 4 tracks licensing which is very good as per my opinion)
Ronin M or equivalent gimbal mounted on the rope is another option.
Yes, you are correct, cropping 1080p part of 4K original will get you 2x focal length equivalent.
Personally I like this source of Royalty Free and reasonably priced music http://tiny.cc/Royalty_Free_Music
Yes I always used nightly beta builds. Not experienced any issues except few freezes very rare.