[Harmony♥]

Hey Blue!
I greatly admire your courage that you have going into a pregnancy at such a young age. I can't even imagine what it would be like to find out I was pregnant at just 12!
Let's start off with you what you called shared custody of your child if you were to put your baby up for adoption: This is called Open Adoption. You don't share custody of your baby however. When dealing with adoption, you are automatically giving your child to a new family. However, if you chose to do an open adoption, you can receive photo updates, phone calls, letters, and even visits with your baby. But, these are all up to your babies new parents. You will no longer be Mom to that child, therefore you have no say when you can and cannot see the baby. An adoption agency will be able to tell you more and give you portfolio's on families that are willing to do open adoptions, however, a lot are not and would rather do a Closed Adoption where you have no contact with the child or it's new family.
I also admire the fact that you have a job at just 12 years old. Sadly, a part time job is not going to give you enough money to rent your own place, PAY that rent, pay your bills and also support a newborn baby. A baby requires lot's of care, therefore, lot's of money is to be spent. There are diapers, formula, clothes (since they grow out of them so quickly), bottles...etc. As well a ton of doctor's visits which you'd need medical insurance for since a doctor's visit isn't cheap these days. It's also true that nobody is going to rent a place to live to a 12 year old, almost 13 year old girl. They'll believe your not responsible enough, and if you can't pay your rent, it's possible that you and your child could end up living alone in the streets.
Don't get me wrong, I'm not trying to scare you. I'm just trying to tell you the realities of your situation.
As for abortion, I'm fairly sure that since you are a minor (under age) that they'd have to inform your parents about the situation. Since you don't want anyone finding out, this would be impossible to do. Of course, I don't know the law's from where you live, so I could be wrong on this part. You might want to get in contact with a doctor's office that specializes in women, a gyno or even a Planned Parenthood. And, of course, abortions aren't free. They cost a lot of money, and are quite painful from what I understand.
I know you don't want to raise a child in the environment in which you were raised, so I'm going to tell you this: TELL SOMEONE ABOUT YOUR FATHER. Your father is abusing you, and no parent or child should have to go through that. Your mother doesn't hate you. She is seeing what your father does to you and is probably scared that if she said anything, she'd get hurt too. Tell a trusted adult: teacher or a counselor, about what is going on at home.
So, you pretty much have your three choices: raise your baby in the environment in which you live now, go through with the abortion, or to choose adoption. At this rate, the open adoption is your best bet for leading a normal teenage life.