So which regret can you live with?
The regret around terminating a pregnancy and the loss of a potential child that you have never met.
OR the regret of having a child that will require your love, care and attention for at least the next 18 - 25 years, that you will be co-parenting with a man who has treated you badly.
The first one, you will be very hurt and sad, but it won't impact on your three existing children. The second one will impact on your three children, and potentially on this baby if their father continues to behave in an immature and manipulative way.
Whatever you decide, I suggest that you don't tell him that you have had a TOP as he will use it as a weapon against you.
I'm so sorry that you are in this position - there is no right or wrong answer. There is just one really hard choice, and neither outcome is going to guarantee you happiness or peace of mind. You just have to make the choice and commit to it and don't waste your time wondering about what could have been.