Invoicing as an auto-entrepreneur to clients in other EU countries

I recently registered as an auto-entrepreneur and have some questions about the specific requirements for French invoices. For the time being, my clients are all located outside France (but within the EU).

1. Do my invoices need to be in French (as well as English), in order to comply with legal requirements in France?

2. I understand that at the end of the invoice there need to be some obligatory details about payment terms (when invoicing professionals), but wish to clarify what these are. As I understand it, they comprise:

• A stipulation of the délai de paiement, which should be 30 days from the end of the month in which the invoice is issued.
• A note about whether there is any discount for early payment.
• The taux de pénalité for late payment. I see there are two ways of calculating this (https://solutions.lesechos.fr/juridique/c/retard-de-paiement-reclamer-des-penalites-a-ses-clients-1604/) I would prefer to go with the lower level (3 x legal French interest rate), since I don’t want to alarm my regular clients who I trust will pay me.
• A note about the indémnité forfaitaire of €40.

Is this correct and if there is anything else I need to add here? Could you also let me know if the following formulation (modified from various versions found online) would be suitable?

Modalités de règlement:
Délai du reglement: 30 jours fin de mois.
Escompte pour paiement anticipé: néant.
Taux de pénalité: en cas de retard de paiement, application d’intérêts de 3 fois le taux légal selon la loi numéro 2008-776 du 4 âout 2008 ainsi qu’une indemnité fofaitaire de €40 due au titre des frais de recouvrement (Art. L441-6 du code du commerce).

3. Regarding the above payment terms, I assume that I do not have to claim these penalties in the case of late payment (one of my best clients is sometimes a little late with payments, but that’s ok with me). Is this correct?

4. As mentioned, I will be invoicing clients outside France (but in the EU). These clients are usually subject to TVA in their countries. As I understand the process, the fact that as an auto-entrepreneur I am not subject to TVA is irrelevant here, since it is the client who is responsible for paying it in their country.
Some sources (e.g. http://es-trad.eu/fr/autoentrepreneur-facturer-a-des-clients-etrangers-bases-dans-un-pays-de-lunion-europeenne/) nonetheless suggest that I need a numéro de TVA intracommunitaire and will need to mention it on my invoices to EU clients (outside France)? Is this correct?
Do I also still need to note my TVA exemption as an auto-entrepreneur on these invoices?

5. Related to 4: do I then need to complete a déclaration européenne de services on the prodouane website? And is it right that I have to do this within a month of sending the invoice?

Sorry for the marathon of questions, but I hope they are all fairly straightforward. Thanks so much for your help!