He sees this as an agreement so that we can save some money yet move on with our lives.
Yeah, no. He sees this as "when the time is right, when she has a bad day, she'll ask me to come back." If you want to move on with your life, you don't want to stay married or financially entangled. My ex tried similar things after the divorce -- it would be cheaper if we shared phone contracts; if I agreed to pay my share, he could keep me on the gym membership (which I would not be able to afford otherwise); we could still order season theater tickets together... yeah, no. I don't think so.