This is a difficult stage for you and also for me. I can foresee this will happen to my H id we move in together. We are due to move in end of this week, but I have given him the option to back out from the deal and has asked him to call the landlord himself but so far he hasnt. If we really move in our Hs will be twins.
I understand when you say now is not the time to give ultimatum yet. I know the feeling of just wanting to give up many many times. People around me also has asked me to just walk away, and he is not worth it. Somehow in my heart I know that I am not ready to do that yet and I am still holding on. There will come a time and place when we really cannot tolerate it anymore and just say enough is enough but maybe NOW is not the time yet.
Hang in there for a while more. I am too. This is the most difficult stage I can say. And maybe if in the end it is just not meant to be, we will be remembered by our children and maybe our Hs (eventually when his head is not too screw up) as the pillar of strength and patience.
Take care..
Sometimes the very thing you're looking for is the one thing you can't see..