Express to your bf that you dislike him and you think he is trying to break you two apart. What makes you think he wants you two to break up? I don't know, but a lot of guys don;t enjoy when their friend's gf is "getting the way". It's not right, but this is the mentality a lot of them have.
tell him about the specific conversations the friend has had with you, so he knows what you are basing this on. don't start with "he is a jerk". Start with, "speaking of so-an-so, there is something that's been bothering me about him. he says these kinds of things to me....."
be clear with your boyfriend about this.
you should not try to get in the middle of something with two buddies; strange thing is, both may end up turning against you; women have sisterhood, and guys have a brotherhood pact. I would let things be, and if your bf is smart, he will call out his friend on his behavior. Unless the friend is making threats to you or being otherwise intrusive towards you, I would not act on it right now.
You got it. just don't spell it.