How do I register as an auto-entrepreneur for a chambre d’hotes?

As previously discussed, we are in the process of me registering as an auto-entepreneur for a chambre d’hotes business - and the lady and CCI is asking the following questions:

1. Quel est votre assurance maladie actuelle ( sécurité sociale ou autre)?
2. Merci de choisir un organisme maladie pour remplacer celui actuel parmi la liste fourni en pièce jointe?
3. Paierez-vous vos cotisations tous les mois ou tous les trois mois?
4. Opterez-vous pour le versement libératoire?

I don’t know what the last question means, but we would like to pay the social contributions three monthly, so I don’t understand what this extra money means?

I know that at present we are with CPAM under the S1 form from the UK but that is due to expire at the end of this year. I don’t know which organisation to choose. The choices are RAM, Harmonie Mutuelle, RMPI and Adrea. I don’t know what the differences are or if it matters which we choose. Also, I understand that we will pay 15% of our income (hopefully to be backdated for our summer earnings for three months, starting in July) in social contributions and we will then declare our total gross earnings in our tax return next May when we may or may not be charged extra income tax.

We are a family of four - myself, my husband and our two small children so have been lead to believe that our income tax threshold will be about 18,000 euros per year, and after that we will pay, but I don’t know at what rate. We also have a gite in the garden which earned 2,500 euros this year, so would like this to be non-professional - is this possible?