I still find it weird to be offering to be more of a babysitting service than trying to come up with a fair/equitable schedule....I think that should be your goal.
I've done nearly all the childcare since the kids were born and with very little help. W then heavily restricted it when she left. I think it was because the kids wanted to come home. At the moment, I see them on a particular day and ask for other days if there is a local event etc. that I would like to take them too. I also go to all of their school events. W today asked if I'd like more days so there is some progress.