Domiciliation & registration of 2 businesss

Hello,

I am about to register a micro-entreprise for an App which will be sold on Apple & Google app stores.  I don’t know how much income this will generate.  Later (within 6-12 months), I hope to also publish an electronic book on Amazon which is unlikely to generate much income. 

1. Our home is in the Var but there are no budget domiciliation options locally so I’ve found a service in Annecy that would scan & forward our mail.  Does it matter where the domiciliation is based?
2. This domiciliation service charges based on amount of postage received/forwarded.  Do you have a feel for the normal flow of paperwork for a basic micro-enterprise?  ie is it dozens a month or should be minimal?
3. I read in one of your posts in Sep 16 that selling an app on the App Store would be considered an activité commerciale, so domiciliation is possible.  Is that still the case?
4. The most appropriate activity code I could find for selling the app was 5821Z - does that sound right?
5. Would I include the selling of the books in my original micro-entrepreneur registration even though it may not start for another year.  Or can it easily be added later. 
6. Would selling of a book also be considered activité commerciale?
7. The most appropriate activity code I could find for selling the app was 5811Z - does that sound right?

Many thanks for your help.