Sounds like you had a lucky escape Mia.
His leaping into a new relationship isn't a reflection on you. It is likely an indicator of his neediness, and probably you're absolutely spot on about him not having resolved the underlying issues. Getting sober is very different from Living Sober and recovery.
I think you need to lick your wounds; thank your lucky stars; and get ready for the next phase of your life. Try to focus on the beginning rather than the end xx