He's exercising more so I think he's gearing up for girl number 2. Good luck to her. He will probably love her enough to defend her though.
He's exercising more because he's also in turmoil, but he's so emotionally damaged that he's unable to recognise that even to himself. So the best way not to think is to keep himself busy. He's let you down because he couldn't face the pressure of standing up to his mother - he's not about to get himself in the same situation again.
He didn't defend you not because he didn't love you enough, as he claims. He didn't defend you because he's incapable of genuinely loving anyone (which means, yes, standing up to people who abuse her, even if they are his parents). He's never going to have a true partner, because he can't accept what that entails - detaching from Mummy. He may end up with a floormat who is similarly damaged or so desperate to be married/have children that she will put up with ANYTHING (though I doubt it). He's never going to become a complete human being, with a fulfilling emotional life, because he doesn't want to. It's easier to ALWAYS STAY WITH MUMMY (think Norman Bates without the psychosis to justify him).
Please stop thinking that any of this is in any way because you were not good enough. HE was not good enough. HE is not man enough to acknowledge how much you are hurting and give you space and time to breather. HE is the one not giving a shit about your feelings.
I know this is really, really tough to accept because it happened to me, but the man you used to be in love never really existed. You have been brave enough to recognise it and act consequently, and have plenty of time to start a good, fulfilling, loving life.
You're the best thing that every happened to him, and on some level he knows it. That's why he's punishing you.