I can't tell from the pictures what type of crank is on the bike or whether you can put smaller rings on it. A lot of France is flat; Eurovelo routes and converted train tracks and canal paths are easy.
I think stealth camping in a foreign country is sort of stupid. Why go to a foreign country to hide in the bushes? There are lots of campgrounds, Aubegres de Jeunesse, gite d'etapes etc.where you can meet people. Strangers are willing to talk to cyclists.