SH, I am very sorry to hear the news. I totally agree that you should get your own lawyer. I also agree that D is just paperwork, and H may come back later. D does free both of you from obligations and to move on. In a sense, you can think of H acting more mature in making the decision and taking the initiative to taking this step (whether he has the "right" reasons or not). You are right that things will change in the future and it is better to get everything on paper rather than "working it out when the time comes". You two can always still "work it out" later.
I am so sorry to hear this. All I want to say is, take care of yourself. Take care.
