FWIW, with respect to complaints about religion and twelve step programs, the complaint is generally the opposite! Working the steps involves surrendering a lot of stuff to a higher power. It is difficult for many non-religious people to find a concept of higher power that works for them.
There are many ways to serve others ahead of yourself without damaging yourself. Indeed, finding a way to be of service to others is a big strategy in climbing out of co-dependence. There are healthy ways to serve others and unhealthy ways. The unhealthy ways aren't good for anyone.
I would think the purpose of turning the other cheek is to forgive and move forward. It doesn't require you to stay stuck, offering one cheek after another, over and over again. Indeed, wouldn't you be enabling harmful behavior of another? That is not loving toward yourself or the other.
Forgiveness and letting go of resentment is a huge part of recovering from codependency. So, no problem there.
And, from what I understand, you will likely find your Christian faith and spirituality greatly affirmed and deepened.
