I won't even say "slow down". I'm saying RUN FOR THE HILLS! There are red flags all over the place here.
*the behaviour he is exhibiting now is WHY the ex won't deal with him. This will be you in her shoes in a few years time.
*This man is verbally abusing you and it should be completely unacceptable to you. And the fact that you tolerate it shows that your self esteem is far too low. Do not make excuses for him. A good man will always treat you well even when the chips are down.
*you cannot love a child who you haven't met and spent time with. Instead, this is about loving the idea of parenting her.
*you may be maternal, but you'd be crazy to willingly take on parenting at the age of 17. Hon, if you are wise you'll spend another 10 years out there working, living, travelling and being treated WELL by men before setting down to parenthood.
*yes, I'm sure there are good parts of the relationship too - even the worst relationships aren't 100% bad. But there is too much bad in this.
I realise that your parents are dysfunctional and not good for advising you. So, try being your own parent. Read this post as if it was your own daughter writing it - what would you advise her? Would you be happy seeing your own daughter moving in with a verbal abuser and wanting to be a mother at 17?
Learn to love yourself more. Don't settle for cr@p like this.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.