How do I turn off the blog and archives?

You are already using pages which does not work the same as posts.

You have to remember, pages don’t have taxonomies and they are excluded from the main query by default on all archive pages and the homepage, so there can never be any links to any kind of archive.

Archive pages, whether date, category or tag archives, are just dummy/virtual “pages” which does not exist. Archive pages are just a way to group posts together which shares a common object. If a grouping object does not exist, the archive page can never exist

To conclude, there will be no links to archive pages that can be “guessed” by robots or humans, it is as I said, they will never exist. Links that does not exist will never be indexed anyway.

And any link in a site that does not exist will simply 404, it will not display blank pages