If he told you that he was done 15 years ago, that could very well be the depression talking. The MLCers say that they have been unhappy one year, two years and even all the way back to when you got married. They truly do not know what is making them so unhappy. Yes, that cold and callous way of presenting themselves is very normal for crisis people. They have to be that way because they do not want us trying to convince them that they are wrong in what they are doing. They truly have no sense of how we feel and quite frankly, at this time, do not care. They want their freedom to seek out that illusive happiness. In their minds, the relationship and us are the problems and that if they can break free of us, then happiness will return. However, they will be happy for a very short period of time and then move on to the next thing to try to see if that happy feeling will return. They will hit that brick wall many times over and once it's done, it's done and hopefully they can begin to heal and face those demons from long ago.
You may be done, but I do not think your situation is over. Please continue to post so that we can assist you in your healing. Come here to vent and express yourself. We are hear for you no matter what.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.