He won't discuss how things will pan out during your Maternity Leave because he knows you will be easy to manipulate,with a Newborn.
You are having a Baby together, a level of planning is needed. You need to decide if you are prepared to leave the relationship. If so, it's ultimatum time.
Pregnant Women need reassurance, unless they are high earners etc. You should be able to get reassurance/support from your partner, or they aren't your Partner.
I can understand you going ahead with the pregnancy, if you want a child and this may be your last chance.
That's something positive to come out of this relationship, anyway.
My Son-in-law was a twat to my DD throughout her pregnancy. They've got back together (I'd rather they never), but deep down she'll never forgive him. It should be a happy time, baring bad news/illness. Your Partner should certainly never be the reason for avoidable stress.
It might be a better outcome for you and the Baby, if you Parent separately.