Superb writeup. One note; a good compromise between entertainment & into and situational awareness might be a single earbud with the radio set to mono. You'll get all the content while still retaining the ability to focus on outside sounds.
Again, I commend you on "letting rubber meet the road" and trying out your GHB. Many guys will "wargame" their pack but never try it until they need it. It was wise to give it a trial run.
Using a single ear-bud is a good suggestion. On the other hand, I had just finished deciding I didn't need the earbuds because my Coby one-piece headphones had worked so well. Back the decision drawing board I guess.
The Coby CV123 headphones I use are a one piece behind the head type. For me they are comfortable and fairly rugged (no foam ear cups to wear out, no thin plastic joints to get broken or crushed). The one-piece design means they stay on and don't work there way out over time. Also the behind the head design doesn't interfere with hats. A previous pair I purchased about 5 years ago are still going strong. Coby is one of those very bottom tier electronics companies that I generally stay away from. These headphones are the exception. I doubt everyone would like them, but they work well for me.