darn. that's a tough one. i don't know what the right answer is, but i do know what helped me a little when i was in a similar situation. i don't know if i was in love with the guy, but i certainly loved everything about him. he was, also, a phenomenal friend, who at one point i thought was into me too, but later began dating someone else out of the blue. it crushed me, every time i saw him i wanted to cry or just ask why. every time he did something nice for me it was like being stabbed in the chest.
anyway, what ended up happening is that he moved away and i didn't see him for an entire year. i had limited my time with him a little anyway, just because it was so painful to be around him, especially when his girlfriend was around (she unfortunately did not live in another country and actually lived very close, so it was hard to avoid them). we were still good friends though, but after he moved we chatted occasionally, mostly online, but not about anything serious, and really, not very often. partly because it was hard for me, and partly because the separation just made it difficult. over time though, the separation really did help. the friendship became less intense, less magical, more casual and lighthearted. he still knew exactly how to make me smile, but it made me happy that he did. And even when it came to his girlfriend, after a year, i could really say, if it made him happy, then i was glad.
i have to say though, after a year, when were both back home again to visit our families and we decided to hang out, i was a wreck. i thought the moment i saw him, everything, all the pain would come flooding back. to my surprise though, while it was still in the back of my mind, it was just nice to see him again. it was just nice to have him in my life, and i really didn't need anything more than that.
so, the separation path worked for me. i don't know if it's the right or wrong thing to do, i feel like you should do whatever you feel you really need, and if that's to get away, it might be nice to get a little perspective on things. you don't necessarily have to cut off all contact with him, but limit it, be too busy to talk all the time, distract yourself so that you're mind doesn't take over with thoughts of him. if he's a good friend, he won't be loss by limited communication. it's like those friends that are so amazing you can not talk to them for ages and when you start again, it's like you never stopped.
It will work out though, whatever happens, whatever you choose to do, it'll be hard, but time really does heal. i'm sorry that you're in the thick of it, unrequited love's a *****. i wish you the best :)