A.The state she resides in now is where you will need legal help should you need/choose to seek further…
The law for custody issues has a countrywide uniform requirement for 6 months residency in the new state before possible to file for custody and parenting issues. How this would apply to pregnancies, I'm not a lawyer, though I suspect legally the legal requirements kick in only upon birth.
B. You are entitled to 50% custody but not really until after infancy and then be careful what you ask for in the parenting plan as it’s often difficult to change.
I've often advocated that from the very start, especially in court filings and appearances, that you don't hamstring yourself to limited or minimal parenting and custodial authority. For example, "Your honor, I am convinced - and am seeking - substantial, even majority custody and parenting time for the interests of our child. While the decision for how much involvement I am granted rests with the court, based on the history and current parental struggles, I am concerned that we may be back in court over the years to come to resolve continuing or new obstructions to my parenting to the detriment of our child."
If it come to this, make efforts to obtain the best (or least bad) outcome from the very first temporary order. Why? If you go soft - perhaps trying to appease and not inflame - and end up with a minimal temp order to start, you will have a hard time or more time getting it improved, thus put effort in to getting the best temp order from the start.
Anticipate objections and obstructions. For example, perhaps mother may insist she can't part with the child because she is breastfeeding. That does not block exchanges because mother can pump her milk, and pass it along at exchanges.
Last thought, do not share your legal strategies with the child's mother. That would likely just enable her to invent counter strategies.