In fact, I will go a step further and reveal the fact that I've thought about "cutting my losses" and simply fulfill 'only' my legal obligations which is 'only' paying monthly child support because the literal hades her residential father and stepmother put both of us through really felt like the best option.
My unconditional love for my child has been truly tested and for a while, I seriously considered taking the easy way out because my constant engagement was/is literally a handicap in my ability to live a happy, peaceful life.
Everyone handles their bereavement over the loss of their child (and don't fool yourselves, it is a traumatic and emotionally shattering loss) and the way they are now treated as a second class parent to their child differently. Some have the strength to weather custodial parents who mismanage their authority and influence and some, really can't emotionally handle it without losing themselves too.
I chose to persevere simply because the alternative was to face a deeply hurt, handicapped adult child asking me "why" and my answer "for self-preservation" would have never been an answer adequate enough to cover the damage it caused her.
It would be more painful for me to have to answer that question later than it is to endure her father's abuse of his residential influence over her relationship with me in her formative years. The later is the lesser of the two evils for me.
Parents are living, breathing human beings not robots.