How do I register as an Artist in France?

I want to register as an artist in France. I will be producing ceramic sculpture. I have browsed through the replies you have given to previous questions, and also trawled through the morass (a complicated or confused situation) of the web; everything seems to suggest the following:

It is necessary to register as an artist libre (BNC non professionnel) with the local Impots. I can just turn up, express my wish to register, and they will do the rest. Will they require me to present any paperwork at the time? All being well, they will send me a siret number in due course, which allows me to sell my art.

Any income derived from my art activities is declared directly to the Impots on my yearly tax return, under revenu non professionnels. Assuming that this income does not go over a certain threshold (approximately 8,500 euros per year?), then that’s all I need to do, in perpetuity. If my income goes over that threshold, then (after the first year) I need to join Maison des Artistes, who will arrange my social charges (15%, or thereabouts?).

1. Is this correct?
2. I currently have a carte vitale by virtue of being an ayant droit (through my partner). Am I right in thinking this will just carry on as it is now?
3. If I reach the threshold, and start paying social charges through Maison des Artistes, will that have any effect on my carte vitale?
4. Finally, is it possible to register as an artist libre online yet in France, or is it still necessary to turn up to the Impots in person? I already complete my annual tax return online (currently, a grand sum of zero).