Thanks for sending the image along - this really helps me understand the issue.  Sorry for your loss - that looks like it was a beautiful tree. However, it now appears very unbalanced, and since the remaining part of the crown leans towards your house, this should be a great concern.

I'm not sure I agree the tree will die, but it certainly will be structurally compromised.  There really isn't much you can do as far as bracing this tree as far as I can see from the photo.  I suppose it would be possible to cable it back to another tree in the area, but this isn't a step you would take lightly.  Cabling and bracing a tree means you have to maintain that...you can't just put it in and leave it.

I suggest that you have a consulting arborist give you an opinion on this.  Visit www.pnwisa.org for a list of people who should be able to help you.