Congratulations on your new baby!
In my opinion, the best thing to do is to get custody and child support squared away as quickly as possible. Until he's established paternity, he has no legal right to take the baby (though I would argue that unless he's dangerous, he has an ethical right). Was he with you for the birth? If he was, he may have signed the birth certificate. That's the first step. From there, getting a visitation schedule requires filing a motion in court-- this typically also includes child support orders.
Typically, judges will not order overnights for a newborn (that usually starts between 2 - 3 years). Short frequent visits are usually preferred for babies.
What kind of guy is he? Is he abusive, an addict, dangerous, or somebody that you really want to keep out of your life for legitimate reasons? If so, he technically has no legal right to the baby. If you don't want child support from him, you can wait for him to file for visitation, and if he never does it, he's basically got no rights to the child.
On the other hand, if he's basically a decent human being, I would certainly encourage you to help him build a relationship with the baby. Even if you two don't get along, he may still be a pretty good father, and he deserves a chance at a relationship with the baby. I would encourage you to invite him over for short frequent visits (say, two hours twice a week?). If you can do it at your house, fantastic. You can help him learn how to care for the baby, and it would give you some time to read a book, take a shower, take a nap, get the laundry done, whatever. And when you do go before a judge for custody, it will look a whole lot better if you helped foster that relationship (again, barring abuse, substance abuse, etc). And if you can get a cordial coparenting relationship going (again, barring abuse) it will make everyone's life, including the baby's, a whole lot better in the long run.
I would also try hard to explain to the baby's father why it's so important to breastfeed. Ultimately, you will probably have to compromise with pumping, though you may very well be able to avoid it for at least the first six months.
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