I recommend two things: Couples counseling and mediation.

Couples counseling will help the two of you work things out and learn to communicate so that even if you go through with plans to separate, you'll be able to put your daughter's best interests at heart and treat each other with respect.

Mediation will focus on what's best for everyone involved while also attempting to be fair and impartial about the situations with which a divorcing couple with children is usually faced. Custody, visitation, child support and so on ~ all can be dealt with calmly and rationally if the couple is willing to work with each other and accept the mediator's recommendations.

Good luck to all of you.