We have a 2 year old daughter. Cutting contact isn't an option
I can't give anyone advice on marriage or relationships, but I can tell you about a terrible divorce. I got divorced 40 years ago, had 2 beautiful daughters, I couldn't handle the marriage and a total nervous breakdown, not a bit of one, total breakdown, whilst still married, attempted suicide 3 times, got very ill. managed to get back on track but the marriage was a disaster. I loved the women and still think about those times everyday.
The only way I could survive was to leave Preston, and get as far from home as possible, when divorced I tried everything to keep my relationship going with the children, they came to London twice a year, I used to finish work on Friday, jump in the car and drive to Preston to see the kids, went on for a long time, I had turned my life around was successful sort of, met other women and lived with them, made successful businesses and life was ok, but the first love and the kids were always there in the back of mind.
Divorce for me was heart wrenching, and devastating, but I survived, it takes a lot of pain and acceptance of the reality that engulfs you. I can't give you any advice on how to cope with it, as it is difficult if you love someone. Today I rarely see my children, I haven't seen my grandson, only photos, one daughter no longer speaks to me. The good thing is my current lady - I have been with for 25 years and we have our ups and downs, but nothing to threaten our relationship and things worked out.
Thing is in life, you never know what will happen to you, there is always sadness and pain, good times and grief, as life goes on you can never predict the outcome, it's about living with yourself and learning from mistakes. A toxic relationship will never work and can hold you back, with devastating consequences. Your child is always yours and if you stay in touch or not, she will get her own life, but you can maintain the contact as she is growing up, try keep it friendly with your partner for your child's sake.
There is the other option, I read once a quote from Sir Anthony Hopkins, he said
'Why love if losing hurts so much? I have no answers anymore; only the life I have lived. The pain now is part of the happiness then.'
Good luck, stay strong, and life might seem shit at this moment, but it will get better concentrate on yourself and your happiness, it isn't reliant on someone else.