I used only the Cicerone guide when I walked. I didn't use the MMDD - I looked at the copies that every Tourist Office has on hand if I needed it. I found the Cicerone guide useful and VERY explicit. Maps are not good - just a sketch really, but the words make up for it, but neither are they very clear with the MMDD either. I took some photo copies of the relevant pages from the road atlas which I binned as I finished them, and they were useful a couple of times - particularly useful for naming towns etc in the distance that don't get a mention in any guides.
I walked in August (began on the 5th) and only had 2 rainy days - more showers, and the rest was hot and humid - even on the Aubrac! Heavy thundery clowds would appear every afternoon (and occasionally thunder) but usually no rain.
Market days are often listed in ordinary guides for the bigger towns. Guides such as the DK guides, Frommers, Michelin, Lonely Planet etc. They are useful to read just to get oddball answers to oddball questions that you might not have thought about! I check each guide before I go and list things like that on my itinerary. The other thing is the internet. There is one website that you can type in the name of the town, get the popluation, and other information. Also try the tourist office websites for the specific towns - they usually have info like that. It is time consuming but you find out other info you may not find anywhere else.
question 5 - I wouldn't worry too much about repair kits. You are not going to a third would country and so long as you start off with good gear there should be no difficulties - and if there is you can usually find a shop withing a couple of days at least (and just manage in the meantime). Though I use duct tape for repairs when bush walking I have never bothered to take it with me on the Camino, Cheers, Janet