Radiant,
It is a blessing that you can see what the email really is about. He is pulling at your heart strings hoping to open up the lines of communication, for what purpose? I am sure that with your long history, he is hurting as well. I think the alcohol affects them more than us in the end. They lose everything and are left to battle the effects of long term alcohol abuse. However, they are so good at putting on the "I am okay, everything is okay" face.
My ex ABF also seems just as happy-go-lucky as he has always appeared on the outside. Now that I am not intimately involved in his day, all I see is that side of him- the one that everyone sees and embraces. However, I know what the secrets are. I don't have to see them to know that they didn't just abruptly stop being part of his life simply because I am not there to witness them.
Helping your parents is a nice thing, of course his motive may not be so pure. Even when you put up your boundaries, you can only control your behavior. I have read that we should also be able to control our feelings and thoughts, but is something that I am still struggling to do. So, until my heart and mind catch up with my determination to have a safe and healthy life, I have to celebrate the no contact and my reactions or behavior when I do find myself engaged with him...time will help. I am sorry about your doggy though. I am sure you miss him. HUGS!!! stay strong!