Sorry for not responding to you quicker, I really wanted to know, but was very distracted with people coming into town and haven't been super active online.
Okay, so, first of all, he obviously had no right to get angry at Abby because he wanted to try and have a relationship with her and she said no. It happens. Either there's chemistry or there's not. There's nothing he can do about it. But sure, I'm positive that him yelling at Abby and calling her names will totally make him more appealing. Works every time! So, even if you didn't know Abby at all, he's already acting like a total jerk.
He's also just being a jerk to you. Even if he really did love her, he could have at least been honest about to you. I'd be a lot more receptive (though still apprehensive) to someone saying to me "I really love her, please just let me have this one shot" with a girl I had history with than him not telling me at all. There's a lot better ways he could have done this to be more respectful to you. Though, it seems his "one shot" failed pretty spectacularly. So now he managed to basically be a dick to every party involved. Woo pure selfishness, I guess.
Also, what the crap? "I'm still in love with her, so now I can't be friends with you, either?" Okay, it's one thing for things to be awkward with the item of your unrequited affection. That's a given. But him taking it up on you is something else entirely, because he could have tried to make amends with you. It'd have been so easy for him to say that he at least wanted to try. I suppose this largely depends on what history you had with Abby, of course, but still, he definitely could've made amends. If he went behind your back for a shot at romance, it failed, and he apologized to you, I'd be mad at him for a little while for doing that, but I'd forgive him eventually. But hey, I'm a romantic.
The fact of the matter is that he obviously doesn't care enough about you or her. This really isn't love when it's all very self-centered like that. Maybe he'll get over it in a month or two. In fact, I think that could be a possibility. But at the end of the day, don't be sad if someone like that doesn't want to talk to you anymore. Loyalty is not something inherent that you need to abide by. Definitely try to talk to him, try to be polite, and maybe he will respond to that and eventually come back to reality. But, if he doesn't, don't beat yourself up over it. It hurts to stop talking to an old friend like that, I know, but stick to people who actually care about your well-being, not people that you've been around the longest.
I'd like to announce that I am back on the internet much more consistently now, so you get much more Chaos's Relationship Advice Train™, now with much more unpredictability, and possibly spikes.
Oh, who am I kidding. There will definitely be spikes.