MacBook – Unlock keychain with Touch ID

This usually happens when you change your login password without changing your keychain password.

1. Open Keychain Access
2. Click Edit -> Change Password for Keychain 'Login'
3. Match the password to the one you log into the computer with.

If you firmly believe "this is not the problem", please try to delete your keychain and recreate it in order to get the link between the login and keychain to properly function. (thanks @dragon788)

Yes.

Apple has published a guide - KeychainTouchID: Using Touch ID with Keychain and LocalAuthentication for integrating Keychain with Touch ID. This means 3rd party developers can create code that allows users to authenticate to their app (an even possibly their website) via the Touch ID mechanism with credentials stored in Keychain

Additionally, more info can be found in the LocalAuthentication documentation

As for the Touch Bar... Adobe Photoshop currently support it.

According to the macOS Human Interface Guidlines, third party developers will be able to design their apps to use the Touch bar. Links to the API documentation and sample code are included. So, it's only a matter of time before apps get updated to support the new bar.