Tell us about yourself!
I would not use a heating device with a flame. It is potentially harmful to some components. A 1500W heat gun works very well. Yea, definitely avoid boards that are conformal coated or potted.
A nice arduino project, but...sigh...like almost every other arduino project everyone does wiring diagrams and NOT schematics. I guess it is the mindset of the community - we just wire boards together, we don't design circuits...
Some good tips about packing with respect to center of mass (gravity) and packing heavy things closer to your body and away from the outside of the pack. The sleeping bag at the bottom is a no-no primarily for ease of access. The best guard against this problem is to get a pack that has a bag compartment at the bottom so one doesn't have to disassemble the entire pack to get to the sleeping bag. I've learned from many years of backpacking, put your sleeping bag in a plastic bag to keep it dry and dirt free - a kitchen trash can bag or a 2-3mil garden trash bag works well and adds almost no weight. Left unsaid, but extremely important - make sure you have a pack that fits well - some good pointers on the net about how to fit a pack.
Aside from continously dealing with ice R&R, the other problem with this approach is that this method adds quite a bit of moisture to the air. The downside of this is that the more humidity the air contains, it feels less cool and confortable..