Family law is littered with the corpses of fathers who tried to be nice to a gatekeeping mother. It does not work. Not only does it not work with the mothers, it does not even work with the judges. They routinely rule against fathers who acquiesced to a mother's demands.
A mother who is denying parenting time because she is breastfeeding a kid who is over a year old is a major threat to the father. He needs to propose a specific schedule that leads to 50/50 sharing. Anything vague and he will never get custody.
The mother agrees to 50/50 in the future, or she needs to be fought in court. This mother is refusing to provide pumped breast milk. We are not idiots, she obviously does not care about the kid at all, this is just a tactic.
Obviously the legal argument is something along the lines of "it is in the best interests of the child to have a shared custody arrangement, and here is my proposed schedule that implements it fully by the time the kid is 2. If the mother feels that breast milk is important, I am more than willing to feed the kid Mom's expressed milk. In the alternative, I am willing to consider a schedule proposed by the mother that leads to shared 50% custody".
Tactically, I would chuck the breast milk and feed the kid formula so he gets used to other stuff. Or, y'know, solid food like most 14 month kids can easily handle. Mom can't prove that you aren't using her milk. (Actually, the solid thing is a little trickier, it changes the poop. Maybe don't feed the solid stuff yet.) Formula and cow milk for the win. Breast milk is not some magical elixir of awesomeness. For the first few months, it provides lots of value, after that it's just convenient and cheap.
The science behind breast milk vs. other food after 6 months is ridiculously weak. No amount of propaganda can affect that sadly.
