There are plug-ins to do that sort of thing – search for “maintenance”.
I have a similar problem with my site not logging in automatically after I changed the url. I found that I could login via /wp-login, but not via /wp-admin. Have you tried that ?
I think I’m having the same problem … let’s hope I get the same solution !
Do you mean that you lose the admin toolbar, even though the checkbox is checked in your profile ?
Ooooh, that sounds scary. Is it normal to have to create your own (child) theme, rather than being able to use one out of the box ? I had hoped to be able to get loads of content on the site and then try different themes.