SSH key will not permanently add to my keychain

One solution is to add the command in ~/.profile or ~/.bashrc file. Then every time you open a new terminal the command will be executed automatically.
Since you are using zsh you will need to add the command to ~/.zprofile or ~/.zshrc file.

ssh-add -K ~/.ssh/id_rsa &> /dev/null

The &> /dev/null is to avoid seeing the Identity added message everytime you open a new terminal window.

Can try ssh-add -K again or edit your ~/.ssh/config to enable the option:

Host * UseKeychain yes

If ssh-add states could not connect, try setting it up with:

eval $(ssh-agent)

Similar to: https://superuser.com/a/1158050