In my opinion the sit start does nothing to raise the difficulty, so the grade of 6b/6b+ is ok. Absolutely good also for smaller climbers: instead of dyno to the right, i got my left foot high up on the good hold - left hand to little crimp - then right to jug.
Rain sucks, but broken holds suck even more. Remember, never climb on wet rock in Fontainebleau.
The sandstone becomes brittle, and pulling on it will ruin classic problems. Drying it doesn't help, because it's still wet and weak inside.
All you can do is wait for better conditions.