In the "Big Book" of Alcoholics Anonymous they call it the "miracle of reconcilliation". Although this is not a drinking issue there are many parallels between the recovery programs for both. In many ways cancer is like a "tornado roaring through the lives" of the caregivers. I would view that fact that he is even showing up for counseling as a positive step. Allow him a little more grace (and space) to get over his resentments. The normal grieiving process can take anywhere between 6 months and several years.
Think baby steps.

It's been said here many times that you can be cancer free but you are never free fron cancer. It's bad enough for a spouse to watch their beloved go through this and then add on their own mortality fears as well. Not even getting into the shattered dreams, fortunes, etc. Give it some breathing space and trust that God has a perfect plan for this.

Focus on what can be changed in you and not him. Stay out of the future and take it one day at a time.