Hugs to the OP.
For what my opinion is worth

here's what I would do at this point:
I think if you try to completely hault all communication with this boy your daughter could rebel, however, I do feel that cutting off the communication should be your ultimate goal over course of the next few weeks.
Somehow, someway cut the phone calls down from daily, to a few times a week, even if it means getting your DD out of house when you know he is going to be calling. Eventually, make it difficult for them to even be in phone contact. Screen calls if you have to. (she's in the bathroom, she's outside, whatever!)
Keep a close monitor on the computer & the IM'ing. Do you know his screen name? Speaking from experience, teens will immediately minimize a "conversation" when a parent walks in the room. Our rule is "if you minimize it, you are trying to hide something, therefore, you are done with the computer for the rest of the day".
Don't come outright & tell your DD that you are trying to cut off communication with the boy, just gradually do it. Get her involved in other activites & with other friends.
As much as you feel bad for this boy, it is not your job to rescue him. From what you have said, I believe if you continue to try & rescue him, it could backfire & you could eventually be helping your daughter make a decision of whether to keep a baby, abort it or give it up for adoption (I know, a little harsh, but reality).
I also don't think this boy should be there when your DH is told what they have done. What is there to gain from that? This boy has enough problems, obviously, without having to deal with your DH's reaction, which probably won't be positive!
Good luck with everything. Keep the lines of communication open with your DD, but get her out of this situation - fast. Nothing good can come of it.