Well it seems to me that your story is pretty self explanatory. He has had some time to live his life without you and now he has some perspective on things so if you two should happen to get back together im willing to bet it would be alot better than before. You should really just talk to him about all your concerns and feelings toward him. Tell him how much he hurt you last time and hear his view on things.
And lastly but most importantly take things slowly, especially this time around because i think you have alot more at stake than last time.
Best of luck
-------
So why did I do it? I could offer a million answers, all false.
The truth is that I'm a bad person, but that's going to change.
I'm going to change.