Fueling shouldn't be a problem, they have fuel stations on long swims such as the Dart 10k. I will watch how it goes with interest. Someone from my swim group (a regular 10k swimmer and IM) thinks it will be harder than a regular IM but its certainly an interesting concept.
Honk - I'm with you on a lot of the drills. I wasted so much time doing drills that did nothing for my stroke. And I include in that the early TI drills I did, although I'm a big advocate of TI and go to a TI masters group. My swimming came together once I'd started full stroke and now have "focal points". So I still do drills, but they are isolated parts of the stroke that I repeat for muscle memory and timing. Things like tapping the shoulder drills or kicking with a board do nothing to help me at all. But that's just me, not saying that would be true for everyone.
Open water can be scarey to begin with. Some people take to it straight off, others not. Its worth for the first time just taking time to get used to it. Swim the smallest loop in the lake or just out to the first bouy and back. Find something on the horizen to aim for - a tree or similar. Try and get a lesson on how to sight and go with a friend first time. Where abouts do you live?
You don't need to tread water if wearing a wettie. Well done for learning to relax - do the same in open water and you will just float upright. Honest! Yes you will splutter and cough sometimes but it doesn't matter, you don't drown in the pool so you wont drown in the lake. Just stop, refocus and get going again.
Sounds like you are starting well to me. I got in the bad habit of only breathing to one side and now I'm having to force myself to breathe to my "bad" side.