I would reply to him in similar vein:
Dear Ex
I am glad to hear that you have used this time apart to realise and regret your own inadequacies as a partner. I am pleased that you understand that our split was entirely your fault and that your behaviour towards me was unacceptable. I appreciate and accept your apology, as I also blame you completely.
This space has also given me chance to have a long hard look at myself and my life and to realise that I spent many years loving you and waiting for you to show me love back. I realise that although I have had my own problems, you are the one person that I should have been able to rely on for help, support and understanding but actually all you did was sap my confidence and make my problems worse.
Much as I might enjoy seeing you on your knees I will not be taking you back. I don't need you to make me happy every day, since you left I have BEEN happy every day because you have not been around to suck the joy out of my life.
I too feel like I have been through a train wreck, but I consider myself to be the lucky survivor who walked away with barely a scratch.
I will always have affection for you and I carry some happy memories from the time we shared, but you loving me deeply is irrelevant because I do not love you at all.
I do not think at this point that we can be friends, although that may come at some time in the future. The wounds you inflicted are still too raw, and although I can forgive you I cannot forget and I will not go back.
Wishing you a happy life.