he will want to see his daughter very often, maybe half of the time.
That he might want equal time doesn't mean he will get it. While there are some states who start with the concept of equal time, you can easily ask for a court ordered psych eval or even a more in depth custody evaluation. The results should indicate to the court that your concerns for the child has basis. (Document now in case you will need to refer to specific incidents. Having record of specific incidents or pattern of minimal parenting involvement helps counteract the "he said, she said" complaints that courts could be inclined to view and ignore as typical bickering.)
Since I was pregnant, my boyfriend changed his behaviour towards me. I am criticized, belittled and browbeaten all way long. He's using all his rhetorical skills to make me do what he wants and I feel mentally abused.
The relationship's dynamic changed. Now it's not just you, there's two and he's having a hard time dealing with it. What a court would view as mental abuse may depend on what the court or social services agencies deem as abuse, how much it impacts the child, how recent the poor behaviors were, etc. However the court system was set up not to preserve relationships, they generally don't deal with that, they deal with the people as they are, so what they do is manage the unwinding of a relationship.
I am at the end of my tether and thinking about leaving. But I fear so much his reaction.
Would you rather handle "his reaction" sooner or later? Odds are that unless he is in meaningful therapy and he is diligently applying it for years then these issues will not vanish, rather, they're actually likely to get worse over time. So if he's unlikely to get effective help, then it is up to you to find another solution. Do you see any advantage to delaying a solution?
That you have these concerns indicates there are serious problems with the relationship. Side point, I would suggest you be sure that you're in charge of contraception. If having one child causes these concerns about the father, two or three children won't make it better, in fact it would make separation that much more complicated.
So I want to ask you, if you ever regret having separated from your partners with whom you share kids? Most of you will have continued fights with your ex-partners about the children, maybe about custody questions.
So, a strategy might be not to go for full custody, hand her over to him as much as he likes and just wait until his endurance for childcare fades.
Distance + Time = Better ... .One result of separation is that the distance apart often reduces the conflict, perhaps not at first but generally the conflict does reduce over time. Yes, there would still be occasional flareups but much reduced than if you hadn't ended the troubled relationship.
As for whether to seek full custody or not, it may be possible to strategize. Courts sometimes split custody issues into two categories: legal custody and parenting time schedules. You could seek majority time and express your concerns about the extent of his parenting time while keeping the 'custody' issue separate from the schedule. They're generally not inclined to grant full custody unless they see incidents, not just risks, of substantive child abuse. Since there would likely be impasses on the major custody decisions, one approach might be to seek to have joint custody modified with you having
Decision Making or
Tie Breaker status. He will still have joint custody in title but you wouldn't have to go to court every time he obstructs or disagrees. He could still disagree and take you to court or mediation, but (1) it wouldn't delay you and (2) it would be him going to court, not you, and not delaying your actions.
Based on the stories that make it here, disordered fathers are more likely to fade into the background than disordered mothers. So yes he might fade away over time but you can't count on the averages. Have more than one strategy to attain good parenting. Make a log of how much time and effort he spends with his daughter. By the time the legal teams get involved you would probably have a long history of majority parenting and so you wouldn't have to feel inclined to "hand her over to him as much as he likes and just wait until his endurance for childcare fades." As my Custody Evaluator told me at our first session, history of parenting time means a lot.