Hello MVin and welcome.
I'm sorry to hear about your dad's diagnosis. Those who responded to you above have given some excellent suggestions. Here's a quick summary of some things are important:
1. Testing for biomarkers to see if he's a candidate for targeted therapy or immunotherapy.
2. Being sure he's getting enough to eat.
3. Is your dad's goal the same as yours?
4. Predicting life expetancy is not an exact science. Many live much longer than predicted and have good quality of life.
All that being said, I think that how your dad tolerates the chemo (or any other treatment) . is crucial. I don't think you'll necessarily know during the actual infusion. Side effects occur days later and can get worse over time. My mom had stage 4 breast can and had radiation to bone mets, which helped a lot with her pain. She also had long term chemo, which did keep her cancer in check, but the side effect of neuropathy gradually got worse and when it became intorlerable to her, she chose to discontinue treatment. Some people do fine with long term treatment, though, so if your father choses to have chemo, it's a matter of how he feels from it and whether it's working.
Best wishes to you both,