Hey RMG. I have to admit that I don't know your sitch, so please forgive my ignorance in advance.
So..what was the point of this email? Was it supposed to provide you with some type of closure? If so, that's fine. However, if it is, a response shouldn't really matter. So I get the feeling that it is more pursuing than anything else.
Also...big picture here...you mention a lot of things that you should or should not have done. But perhaps the problem isn't that you didn't do A,B & C...but that you should have been more agressive, followed through on things, and been more supportive. Because those things are kind of symptoms of these. Does that makes any sense?