it took us until about page 13 for the real point to be raised here: informed consent
we spend hours, i hope, drumming this into our daughters and sons. Really hammering the point home. This pregnancy, condom failure aside, is the result of sex without informed consent by the man. (boot on the other foot is tempting to say "tough tits, mate, you know how many women a year this affects?")
So only the legal questions need to be answered really. Legally? He must pay. He can opt to pay more than the CSA minimum, my guess is he won't and that to get even that the OP is going to have to go to CSA and get the ball rolling. The sooner the better.
Moral questions? if you have fully informed PIV sex then you must accept that one consequence is a child. the man in this scenario didn't want an abortion either (but if it were the other way round and OP wanted an abortion, he would have no say, which is as it should be. It is a consequence of being the man in this universe). So once OP was pregnant, barring mishaps, the end result is a child.
Man must pay.
Regarding involvement in the child's life? A quick glance at the step-parenting board will show you that you can't force him to have any physical role in the child's life except to stump up the cash. In this scenario i am wondering if he really did want a child at some unspecified point, but the reality of the situation that he couldn't control panicked him. Plenty of men who theoretically want kids when they're ready have a panic when confronted with an actual pregnancy. And many many of them step up and are great fathers. Some develop into great fathers. Some - not so much.
It's like when one partner admits to an affair. There are many reactions. But one of them, a quite common one, is to give it a go then end the relationship. That may be what happened here. He tried, but couldn't face living with the lie on a daily basis. He may eventually come round and step up and want contact etc. But legally? I don't think OP can force that. Morally? Well of course for the sake of the child he should. But on the other hand, morally he shouldn't be faced with this situation and he's only human.