Glibly yes to all the above with minor caveats.
4. This is not out the box, but there are open source (and commercial) products that can be used.
9. Viewers work by creating a PDF rendition of your documents using LibreOffice. DWG is not out the box but it exists in the add-ons that you can download.
10. Alfresco does not store its documents in the database so max database size is unlikely ever to be an issue. I have no idea what it is but I have seen several comments in these forums about installations with millions of documents (one with 20 million). Note however that the default Alfresco installation is now on PostgreSQL and it may be wise to stick with the default.
6 & 7
6. Is easy. You create a custom document type and make your uploaded documents this type (which you can do by rule) and they can then have any cusotm fields you want. This is also known as custom metadata or properties in Alfresco speak. Custom document types do not change the underlying "type" of a document (i.e. it can be a docx, pdf, dwg etc and have a "document type" of "purchase order").
7. The displays are fully cusomisable and there is lots of extensibility functionality in Alfresco and Share. It will however take a little while for you to get your head round.