Keychain Issue - Yosemite
The "admin" account you set a password for was "System Administrator (root)". You'll either need to type "System Administrator", or "root" as the user name. This "super user" account is part of the operating system, and can do whatever it wants - including things that have extremely negative consequences. I recommend disabling it. See OS X Mountain Lion: Enable and disable the root user[1] for how.

If you want to fix the keychain and can't figure out what password it uses, open Keychain Access and click the "Reset my default keychain" button on the General tab of Preferences. If a problem with "Local Items" occurs after rebooting, see this article.

As for the use of empty passwords, that is probably on purpose. You can't start a new user with no password anymore, and you can't unlock Security and Privacy system preferences without a password.

And finally, Chrome doesn't have a keychain to make use of on other operating systems, so if it can't use the user account's keychain it makes sense to me that it'll fall back on its own internal storage.

[1] It has been the same method for a long time, you can ignore the "Mountain Lion" in the title.