Hi Aurélie, I did it after seeing several videos starting in the crack. I have not seen anyone starting with both hands low. And on bleau.info it is defined as "sit start", which is possible with one pad even if you are small. So ... I think I did it right, but can not be 100 percent certain.
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.