Goal is SASU in France, USA LLC, single customer, dividends, carte vitale, PERIN similar to 401k?

I am currently an employee and a USA resident.  My plan is to become self employed, create a SASU and become a resident of France within this year along with my spouse who is retired.  I would start with at least one customer (my current employer), and another customer that I did work for a few years ago that I should be resuming work for them this year. 

I have a few concerns and questions.

1. I want to be able to invoice my customers and for it to be convenient for them to pay me.  Will they be able to direct deposit into a French bank account?  I am assuming that there will be complications.  If so, would it make sense for me to incorporate an LLC with an associated bank account in the USA to deal with my clients? 

2. I have seen posts that the French govt. will scrutinize a former employee with their former employer as their only customer.  What are the ramifications of this?  I am confident that another former client of mine will be back within the year, but I don’t have a contract with them (yet). 

3. My understanding is that with a SASU you only have to pay %30 flat tax on the dividends.  However, in order to get a carte vitale, you need to have contributed via salary, so it is common to pay a minimal salary to contribute.  Is that correct?

4. I read that there is a French equivalent to a USA 401K in France called a PERIN.  Is there a way I can structure my salary or SASU dividends to deduct taxes and pay into a PERIN?