I agree with you here. From what we're given by Jessica, Christopher is a self-absorbed shit and no woman in her right mind would take him back. But somehow this story worked for me in spite of it all, and is by far my favorite Podcastle to date.
Well, that actually brings up an interesting point. The entire story is from Jessica's point of view and we never actually see Christopher. I'm not saying that Jessica's an unreliable narrator, but she's certainly a biased narrator. She seemed somewhat unaware of her own feelings towards Christopher (the wording the author used to convey something the narrator wasn't aware of was quite well done).
I actually wondered exactly how much of the story had happened and how much was conjecture, although I will admit I found Heather's explanation at the end a bit strange.
I think that Jessica is a bit unreliable. Looking deeper at what she says, it sounds like, for a successful artist, Christopher may be a pretty down to Earth kind of guy. He plays video games, reads comics (and obviously tried to get her to at least understand why), and he gives the woman he loves everything short of the moon, which probably would have been next, just to get her to give him another chance. Yes, he cheated on her while drunk (the vomit being just the icing on the cake), and that is inexcusable, but it is explained by Heather... who may also be a little unreliable.
Jessica on the other hand seems like she's very self-absorbed herself. She's told by everyone who knows them as a couple to give him another chance because they see something in Christopher that she isn't seeing, but she's too concerned with looking weak, with giving an inch and getting nothing in return (save for roses, booze, one of her skis, a sculpture, a fully staffed bar, male genitalia, Saturday, Spain, etc) to even consider it. The woman is so petty that she burned a "tear" spattered note just to prove that the drops were not tears. She (per Heather) drove Christopher into the arms of her own sister by being too cold and judgmental.
At the start of the story Christopher seems like the stereotypical philandering jerk, but as the story progresses I think that we see that's he's not the total bastard he at first appears to be, while Jessica is not the totally innocent little victim in all this. At the start it looks like Jessica has been betrayed by a louse, but by the end we see that she is every bit as bad as Christopher may be, just in her own way.
Now maybe I'm just defending Christopher because I'm a 30 year old who plays video games and reads comics myself, and maybe I'm a self-absorbed shit who is too self-absorbed too notice, but I think there is enough evidence in the story to show that Christopher is not the anti-christ, and that maybe both he and Jessica need to give a little to make their relationship work. Jessica took being right too far, and ended up being in the wrong as well.
I found Heather to just be odd in general, but I think that may be partly because i kept picturing her as Twist from "Spaced".