This seems very simple to me. First off, a conversation and a process when moving from closed to open is not too much to ask, but, well, that's water under the bridge. Let's look instead at where you are now.
A single night between dates is not too much to ask. A single day's notice before a date is not too much to ask.
You know what *is* too much to ask? Reserving the right to complete spontaneity despite having an infant and a partner at home. You can't build a family with no obligation to be there for them reliably. Poly =/= whatever you want whenever you want it.
Either he doesn't know how healthy, reciprocal relationships work or he doesn't care. If I were you I'd offer him one last opportunity to change his ways and then I'd go.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.