ssh: Identity not Loaded from Keychain at Startup
Have you done a ssh-copy-id of your public key to your host? If not the

UseKeychain yes
AddKeysToAgent yes


is meaningless, since the host has no way of verifying who you are, and will ask for the password or passphrase.
Take a look at Taming the terminal part 30/37 for an explanation.
Also man ssh-copy-id should give you more info.