Hi Syndney,
I am sorry to hear that they weren't able to bypass all the blockages. Sometimes after radiation treatment, areas around the heart including the arteries can build up calcium deposits that make surgery difficult.
It is very important that all risk factor modification take place and smoking is very important. I can't really estimate how long this might prolong his life, but it is very important that he does it. This also includes diet, exercise, medications (statins, beta blockers, and potentially ACE inhibitors).
I hope this answers your questions. Good luck and thanks for posting.
My grandmother had a 2nd set of bypasses at 84. She had only 1 native artery available, and the surgeons used a cadaver vein. She's doing well at 90 and her risk factors are very well controlled.