When does the blogspot “day” begin

You must configure your domain and create a CName record that points to ghs.google.com from your subdomain (blog in this case). Then you can use blogger's interface and tell it to use blog.mydomain.com.

The instructions vary by host, but Google has a basic article on this.

An alternative is to use 4 A Name records that point to Google's server's IP addresses.

I have found the articles on the site http://blogging.nitecruzr.net/ informative, just be warned that there are a lot of them and it can get confusing since they all link to each other.

In the Layout function, edit your Pages tab.

I suspect that you will find you have chosen to only show selected Pages, and that the three which are ticked are the ones appearing on your blog. Tick the others, or just select to show all.