Clients in the EU and TVA shifted to recipient

Hi, I have some questions regarding clients in EU and my invoices in general. First of all, let me tell you that I have a TVA intracommunautaire, I’m registered as “6201Z PROGRAMMATION INFORMATIQUE”, and my main client is in Netherlands.

1. The VAT is on me, since on my invoices I’m instructed by the customer to write: “VAT shifted to recipient according to article 44 and 196 of the European VAT Directive”. I’m gonna pass the 32K limit this trimester, so how will I include the TVA in the upcoming invoices, given the TVA is shifted on me according to the previous clause?
2. I’ve never used ProDouanes so far… Is this obligatory? First time I read this in your forum :/ Am I gonna be in trouble?
3. About the obligatory details of the invoice:
3a. Si la facture est adressée à un professionnel => What does it mean by profesionnel? Who falls under this category? My main customer is an EU enterprise.
3b. What happens in the case I have forgotten to include some of the obligatory info and I have already declared my chiffres d’affaires? Can I amend this in my copy of invoice or should/can I do this for my customers as well?
4. About having a personal/professional bank account, does this mean that the account must only be used for my business? Meaning there should be no other “income” shown, like for example a friend sending me money from a personal exchange? Likewise for
5. In impots.gouv.fr, do I need an “espace proffesionnel”? I have a particulier, but I had also opened a proffesional one as I didn’t know what was needed at the beginning. If it’s not needed, can I (and how) close it?
6. About URSSAF, I don’t have an account on their website, and when I go to register a new one, my SIRET number is not recognized (“Votre SIRET n’a pas pu être identifié. Veuillez vérifier votre saisie.”). I tried with the Independant link.

Thanks