The best relationship advice I have seen are these channeled words of God as transcribed and published by Neale Donald Walsch in his book Conversations with God, An Uncommon Dialogue, Book One: “The purpose of a relationship is not to have another who might complete you, but to have another with whom you might share your completeness.” I think that sums up most of what the AAs and you have said very well here.

When I was in rehab 10 years ago and mired in a toxic relationship with a borderline, my therapist asked me to describe what a healthy romantic relationship should look like. Despite being in the opposite, I wrote that each partner should maintain their sense of self; no one should lose who they are to the relationship; it should be a partnership wherein each person maintains their autonomy; kind of like a treaty between, for example, the United States and Canada — contributions and rules are agreed to but each country maintains its sovereignty. This described an interdependent relationship. It is the opposite of codependent.

Despite my description, it took me another year and many consequences to finally break free of that relationship. Here are two tanka I wrote:

You are the greatest
You’re disgusting I hate you
Wait please don’t leave me
Thrives sowing chaos around
Rollercoaster ride from hell

Codependency
Lost self-awareness and worth
Stop eggshell walking
Set and defend boundaries
Proudly assert your power

Regarding doing one's own inner work and that no one can change another person, that, not sobriety, is the core of any 12-step program. I believe that certain of the steps, the ones that don't mention substances and that don’t mention God, should be taught in high school. I describe those steps in the second half of this essay of mine, https://medium.com/know-thyself-heal-thyself/spirituality-redefined-ff45cb53eaf2, subtitled "Plus a program for living a spiritual life." Too many people look for spiritual shortcuts. The inner work of the 12 steps is the same as the voguish term shadow work.