First off, Jeff, I'm very sorry to hear about Marc. My wife Kristin died of complications related to CC last fall, and I'm still having a tough time, so I know the road ahead will not be easy for you. I feel for you, buddy.
It does help, though, to have oncologists who care. When Kristin's learned that she was dying of sepsis and pneumonia rather than the cancer itself, he did not visit her at either the ICU or the hospice, nor did he attend the memorial service. No condolence message from his office. I guess since the cancer wasn't involved, it was no longer his concern, so he just moved her file to the "inactive" drawer and moved on to his living patients. I found that remarkably callous and unfeeling.
Meanwhile, the best advice I received was from a Buddhist friend in the form of a poem by the nature-oriented poet Mary Oliver, and I'll pass it along to you: