Can two domains use the same database?

No, not in the manner that you’re planning on doing it. Everything relating to the site (including the design, selected theme, etc) is stored in the database. By having a second site attach to it, any changes made there will be reflected on the main site.

Getting WordPress to work inside a rails 3 application

I had a similar problem, but handled the VirtualHost configuration in a different way: Used an Apache mod_alias to redirect what for you is /home/blog/ to a path outside of /var/www/railsapp/public/ (e.g., /var/www/wordpress) Then, for that new hosted directory I had to declare PassengerEnabled off to avoid getting the standard rails error message. I’ve wrote … Read more

Secret keys in SCM

Your config file shouldn’t be public at all. It includes your database credentials in addition to the 8 SALTs WordPress. (The secret keys alone make it possible to brute force your log-in in a bout a week: http://codeseekah.com/2012/04/09/why-wordpress-authentication-unique-keys-and-salts-are-important/)

Changing from localhost:8888 to localhost

You need to treat this just like you would when changing domains. The short version is: You need to change the WordPress Address and Site Address in Settings->General. You have to change both Or edit wp-config.php to alter the same values as in step #1. This one is easiest if you’ve already lost part of … Read more