Sorry Annieeeee this is shit.
You've realized by now, I hope, he won't change, he is a selfish bastard.
How can you love him? Maybe your views on love are a bit skewed, maybe you have had bad boyfriends, abusive ones or this is your first love and you want to believe the best.
Maybe the men in your life (family, friends whatever) all acted badly and you expect little else.
I would say you could benefit from counselling to work out why you are willing to accept this kind of shit behavior and call it he is love.
Here is my take...
"basically forcing me to have an abortion." He cannot, it's your body, you choose. Tell him that.
"I should have seen this coming" You should but hindsight is 20/20.
"The way he has been talking about my child.. Saying things like i just want this thing gone. Horrible horrible things. I guess what i am wanting advice on is if you all think i would be best to keep this child and get him to sign over parental rights."
Get counselling, I don't know about signing over parenting rites. Is it legally binding?
" i dont want him coming back in 6 months when he realises he had it good and that the grass isnt necessarily greener" yes, definitely do not take him back.
"...i need to have an abortion then we will have kids when he is ready." If he has managed to impregnate three women in quick succession what would make him feel he is ever ready to take up responsibility?
Get counselling and help, make your choices and do not do so with reference to him. He has chosen to cut himself out of your life. He is not worth it.