i get your fears of how to tell your parents but.. give yourself some credit! both you and your girlfriend have stood up to the call and are doing what you can. and kudos for that.
your parents may be mad at you at beginning but will come around sooner or later. it is their first grandchild on the way and after the initial shock it will get better. they may say things they don't mean at the beginning, as they'll be in shock when you tell them, but try not to give them too much weight.
threatening you financially before something like this happened shows that they still view you as their baby who's dependent on them for survival (maybe because you're the youngest); but you are more than that and you know that!
moving 600 miles away to study and be the first one in your family to do so, stepping up to your responsibility and supporting your GF and your baby, coming here asking for help on how to do the right thing already prove you're on a good way when it comes to dealing with the situation.
if your parents are worried you won't finish college if you become a father, well make sure they understand you are determined to accomplish your goals.
and ultimately - you are not the first sophomore couple who ever got pregnant. it happens all the time.
i remember a friend of mine who got pregnant at 18, she has just finished high school, was about to start a college and unemployed, and back then she didn't even know if her BF would stick around or not... and she came up to her parents, sat them face to face and before they even managed to fury up, she said: this is my decision and there's nothing you can do to make me change it. you can either disagree on it, and i'll make it on my own, we'll spend some years apart in a war against each other, and then sooner or later we'll grow back together when you realize my child is also your family. or you can accept the situation and play along and spare us all those years of unnecessary conflicts and suffering it will take us decades to recover from.
(she floored everybody with this, btw. even to this day i don't know where she found the guts.)
all this to tell you to face them upfront as much as you can, explain them it's tough and that you and your GF have a plan and that they can be a part of it if they want.