Raine, It sounds like the death of Chris was the trigger that started your h's downward spiral. Yes, he's got some other unresolved issues going on, but Chris was a friend and someone who lived in the neighborhood. A person doesn't have to be a close friend for their passing to trigger a crisis for another person.
Your h is afraid of depression and the stigma it creates. He's afraid to go on medication and I'm sure he's afraid of the possible side effects that it may create. Going on and going off the medication on his own could be lethal and create all sorts of issues for a person doing this. Apparently Chris was at the end of his rope (no pun intended) and thought the only way out was death. He may have felt that dying was the only way to have peace and provide peace to his family. I, too, know of a man who did this and he didn't leave a note either and yes, he was suffering from depression as well.
Your h has a lot of issues to deal w/and he may never deal w/all of them. He knows that he's losing a wonderful wife, family and home, but right now, he doesn't know how to fix himself in order to return home. He doesn't know how to be "happy".
You had to set your boundaries and you are sticking to them. You have to have some stability in your home for you and your sons and this is the only way to do so. I commend you for sticking to the boundaries. Raine, you've done everything humanly possible to save your marriage, but now you need to save yourself and your family. Whatever happens down the road, you and your sons will be fine...but it's going to take some time, patience and plenty of love to get to the other side.
Thank you for the update and I hope that you will continue to come back and periodically and let us know how you and your sons are doing.
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.