Multi Activity Auto Entrepreneur registration for Passport Talent

I am an American living in France on a passport talent Visa. I arrived last year around April. I need to set up an auto entrepreneur structure and get my social security set up. I lived in France from 2004-2009 as a assistant de langue, student and then I believe I had a profession liberal visa for a year. I had a carte Vitale back then so I should have a social security number already but don’t know how to find it.

I have multiple activities. I am a writer (for hire for commercial writing), an app developer (software engineer) and I also have sales from apps I have created (eCommerce). I need to register a structure that can encompass all these activities for now and get up to date with any tax payments or charges that needed to be paid (for 2019 if needed and 2020). All my income last year (and so far this year) have come from outside of France.

As of 2020 I have had eCommerce income and writing income from outside of France. I envision having mostly eCommerce income moving forward with a structure based in France.

So questions are:

1. Where do I find my social security number and get a new carte Vitale? RSI?
2. What do I need to set up to embody all my activities?
3. Do I need to register or declare anything for 2019 if all my income came from outside of France?

Merci.