I don't feel qualified to respond to most of your questions, as I have only personal experience to go by and I hate to be a downer by relating only negative aspects of chemo. I think it's so hard to decide for or against chemo because it is so variable and everyone responds differently. You think if you don't try it, you'll kick yourself because MAYBE it could have been that miracle cure that it is for some people. Well, not a CURE, because there really is none, but a prolongation of life. I think I read that chemo has a positive effect on only 30% of cc patients - I may have that number wrong, but it was less than 50%.
The question that was most important to me when deciding about chemo for my mother was whether it would improve her quality of life, or let her have a DECENT quality of life for a while, whether or not it shrunk the hundreds of tumors in her liver. We were told unequivocally that it would improve her quality of life, so we went for it. They were wrong in my mother's case, but for some people the chemo does wonders (many people on this site). My mother only had two rounds of Gemzar and Xeloda for two 2-week cycles and she didn't handle the side effects well. She had a compromised immune system to begin with, and was overly sensitive to most drugs, even aspirin and Pepto Bismol, to name two. What I'm saying is that you may want to take your father's physical tolerance into account - can he tolerate pain well? Does he have adverse reactions to drugs on occasion? I read up on the chemo agents before my mother took them, and found that 90% of people have side effects that are mild and treatable and not too debilitating. This was NOT the case with my mother, unfortunately. Also, anyone over 60 years of age usually has less ability to fight off the effects -- usually. There are a lot of "ifs" and "buts" and it's very frustrating. As far as side effects, the Gemzar was the worst for my mother - made her very nauseous (and the anti-nausea drugs didn't provide complete relief), killed her appetite, which wasn't so great at that point anyway, and made her anemic and short of breath so she had to be hospitalized. I really think the stress to her body made her succumb more quickly. As for the Xeloda, I forget her dosage, but the side effects were initially bad so she had to take a lower dose, then she had few problems. Everything tasted metallic to her, but she didn't have the dreaded hand/foot syndrome that you hear about with Xeloda.
My mother was also stage 4 with her whole liver involved, but they found a couple of very small spots on her lungs that really weren't symptomatic - but would have been over time. So it doesn't need to spread beyond the liver to be debilitating. She never had surgery, however, because it was too late when it was discovered, so your father has a much more positive prognosis.
I think your idea about the CAT scan is the wisest choice right now - and I would hold off on chemo until you feel he's deteriorating in some way. This is just my personal opinion, mind you. If he's still recovering from surgery, it may be better to wait before you put his body through more stress. Then again, he could have bounced back very well from the surgery -- like I said, so much depends on the individual and even then it's hard to predict outcomes. I've heard that Avastin, while somewhat effective, can be very hard on the body and they don't always like to use it on older people for that reason. We put off chemo until my mother started to get uncomfortable symptoms, but in hindsight I wouldn't have done chemo at all - she only lived 2 months after diagnosis and had terrible quality of life. My stepfather died of lung cancer 4 years ago and he adamantly refused any type of chemo, and that made it so much easier for us that he had such a phobia about chemo, so we didn't have to make a choice. You hate to think you're giving up hope by giving up on chemo, but there are many people on this board who swear by natural remedies and foods - carrot juice, mushroom extract, etc. You can try those while you're hashing out the chemo question.
Sorry to ramble on - I'm sure you'll find useful info on this site, and please remember that there is no RIGHT answer, no matter how much information you absorb. I still feel guilty about letting my mother do her last round of chemo when I could have stopped her, but if she didn't do chemo, I'd feel guilty too, so it's a catch-22. What's most important is to respect your father's wishes and keep him informed. And, of course, to be there for him and let him know how much he's loved. He could live another year or another 10 years - and I hope he continues to enjoy good health long after that.
Best of luck to you and your family - let us know how everything turns out. We're all pulling for your father and sending our love -