I mean "drop the rope" completely. You have a daughter together means just speaking when needing to about her. I can't say whether or not this is your next step, I'm just answering the question you asked about what is the last step.
An ultimatum is usually the very last step, but unless you're ready to follow through and walk and live with it not coming down on your side and will move on whichever way it goes, just try letting go completely before you get to that ultimatum point. Let go, move on. If that doesn't do it, then it's not going to happen right now.
