For long runs, I stick to what works for me: dates and nuts. Natural, easy to digest, and provide a boost of energy. I also make sure to fuel up with a balanced meal the night before and stay hydrated throughout the run. No fancy products or gels needed!
I'm with you, treadmill running isn't my favorite either. But it's a great way to get in a run when the weather isn't cooperating. I've found that creating a playlist or listening to music helps me stay motivated. It's not the same as running outdoors, but it's better than skipping a run.
I've dabbled in minimalist shoes, but never fully gone barefoot. I think it's interesting, but not for me. I've got too many miles on my legs to switch now. That being said, I do think it's a great way to improve form and strengthen your feet. Just be careful not to overdo it, especially if you're new to it.