Dear Amoré, you really look so beautiful and feminine in body and psyche. I'm touched by your image.
I've been married twice. Left a first marriage when my daughter was one year. But I was very fortunate and obtained shared care of my daughter (50:50 split) which despite some (serious) ups and downs over the years, worked out extremely well. My daughters an adult now and a very independent/strong character.
Back when I did, I knew I had to leave - I knew I had to jump the gap when the opportunity presented itself, because I sensed I would otherwise become trapped in a marriage with someone I just didn't like as a person - and 16-18 years till a child is an adult, is a long long time (as well as being, as others have already mentioned, a sacrifice about which it is unclear as to whether actually beneficial for children). My experience is that the opportunities to 'jump' soon fade away and might take several years and more heartache to re-present themselves. Also, I sensed that when a child is very young, parents separating can be much less distressing (for them), than when they are 5,6,7,8,9, etc.
I also deeply loved and adored my daughter, and did everything I could to create a situation/environment which I believed the courts would consider suitable for the granting of shared care. At the same time, I do think, that if I had thought my ex would have brought up my daughter really well (i.e. really given her that special attention and devotion and nurturing that a good natural mother can give - the 'golden elixir' of life, so to speak), then I would probably have settled for less than 50%, maybe far less - maybe for nothing - as I believe in certain circumstances, leaving one parent to bring up the child and saving the child from all the stress that 'fighting-it-out' can bring, can also be a gift to the child. I couldn't do that in my circumstances, as I considered my ex to be severely lacking in terms of the love and stability she could provide to my daughter. Rather I knew that was my job to perform. Though I did have representation at times, as far as possible I represented myself in court, as I had neither the financial resources to cover paying for representation, plus I think in family cases, self-representation can provide the court with an opportunity to get more of a sense of an individual.
I know what you mean about going 'round and round' - I always thought it was like pass-the-parcel of bad-emotional energy. Personally, I believe the only way out of the feedback loop, is some time apart, even if for a few days informal weekend break. There is little more true than the saying: time apart makes the heart grow fonder and sometimes more forgiving.
I wonder if in the end, it comes down to whether each of the partners actually like each other. We all get so bound up in huge themes of love and devotion and sacrifice - that 'like' seems such a small almost irrelevant 'sentiment'. But I'm sure it's the most important factor, as when we like someone, and their character and who they are, it's amazing the allowances we can make - but when its missing, there's just no real connection.
best wishes and I hope the new year brings something really special for you.