1. No it doesn't still stand. If a mother's presence is biologically necessary for her child's development in the same way her uterus is necessary for fetal development, then the OP is right and childbirth does innately biologically necessitate that women spend more time with their children than their male partners in the same way that it's a biological fact that fathers do not carry fetuses to term and give birth to them. If their presence is, instead of "ESSENTIAL", "optimal" then my question becomes: "optimal" for what compared to what and for whom? It becomes a case of people and the groups they form making decisions to optimize for certain goals by behaving in a particular way, not raw biology empirically operating.

2. Yes, I did. It didn't seem relevant to the point I was arguing, see #1.

3. For optimal, see 1, and for midwives—yes, and that's a societal trend rather than a biological fact.

4. True but still irrelevant, see #1.

I'm not arguing that biological mothers aren't generally inclined to want to spend more time with their children than their male partners, or that newly born infants aren't going to instinctively want to spend time with their mothers. It's just OP's original claim didn't logically follow from the evidence he presented—nothing about childbirth necessitates women having "the first choice to spend time with those children, and [...] bargaining power in relationships."