I'm not going to discuss the reasons behind this, I'm doing plenty of that elsewhere.
However, when someone has broken your trust so spectacularly, I don't think it is possible to rebuild the trust perfectly. The example I use for children at school is imagine a vase that is perfect. It gets dropped and broken (much like trust when you lie). You can repair it. It will look like a vase again, it might even be a really good job but the weakness will always be there and the cracks will always be visible. It will never be the perfect vase it once was. To continue this, it's up to you whether you want to put a repaired vase out on display, or throw it out. Or a piece of paper that has been screwed up. You can flatten it out and iron it, but it will never be that perfect piece of paper again.
He is also not the one who gets to decide whether it's gone on long enough. Or whether it's being blown out of all proportion.
As for rebuilding trust, I know I couldn't. Which is one of the reasons I'm so definite about my particular deal breakers. I wouldn't want to put myself through the agony of the doubt and the uncertainty. In this case the responsibility for mending the trust is on his head, it's not shared.
I also think CaptainHindsight put it perfectly.
He didn't accidently break your trust. And even if he felt he couldn't say no to the first error in judgement, then went onto make more. That's not someone who was thinking about you or your feelings or felt bad about breaking your trust. That's someone who thought, "fuck it" and then did what they wanted to. And the comments he appears to have made since don't show any greater consideration for you or your feelings than did his original actions.
So is it possible to mend? I don't know. Some people believe it is. I'm pretty black and white on these things.