Hi John,
i cant answer all your questions but i may have some good advice.
1. try websites
http://www.mundicamino.com and
http://www.caminonorte.org
i think the guidbooks from france, the amis st jacques are possibly the best guidebooks ive seen for any trail books in europe. I dont know if they have a guide for this route though, yet.
2. difficulty. this depends on you. are you physically fit? can you handle elevation gain and decrease of some 2000 ft? More hills on the Norte. More hills at the start than at the end so many people will report more difficulty because they are just getting started etc. Mundicamino has a good profile map. all different people walk and so all different people have various reports. your experience will help alot!
3. Dont worry about rain. It only makes a voyage better, the dry days sweeter. Ive hiked over bald mts when 70 mph winds were in the valley. Walked through rain for 25% of my long trail e2e. You have to be more careful but its nice to have a shower while walking. From what i see the gain is stretched out over the course of many km and so shouldnt pose a high threat.
4. The amount of people that finished the Norte last year was around 4500 or so. dont have the exact figure but it similar to the USA appalachian trail. (about 3-4k people a year do this hike) Dont worry, if you go with your heart you will find a friend if you need one and no one if you dont.
5. In my experience as an animal handler, i train dogs actually, any miscommunication can be avoided. I imagine you are frightened if a dog is snarlin/snapping at you. Many dogs do this out of resource guarding, that is they protect things. Use a firm voice with dogs, they will try to intimidate you further and impose dominance upon you if you let them. As a last resort you can carry a stick to try to block the space between you and the dog. From all the journals ive read though you will probably have a dog wanting a friend. They are social creatures and he may be as lonely as you may be. Barking can be for anything from the "hello, pay attention to me, through a ball for me, thats mine, lets play!" etc. When you greet a dog, pet underneath the neck and stroke his head so his eyes go somewhat parrallel to the floor, give hims chance to smell you and you give him one stroke on the back. His body language will tell you if we wants to be petted or left alone. Worst comes to worst you could always carry a doggy treat or to and bribe your way past him!
also hee is a site of journals.
http://www.trailjournals.com some good camino journals, all are in english and oretty sure about the
camino frances.
buen camino,
chris