Hi Bridget,
I am so sorry for the journey your father has found himself on and by extension, your family.
There are some folks on the Johns Hopkins Online Pancreatic Cancer Support Board who have time off from chemo with varying results. Dr. Fine @ Columbia in NYC has said that chemo can be stopped for up to 4 weeks with no growth of tumors. However, that is another of those things that seems to differ with each patient.
There are also patients there who have had or are currently on GTX with good result, although I can't say about side effects. Since the side effects of chemo are cumulative, the fact that your father is feeling worse recently is not out of line.
For many pc patients there comes a point where a decision must be made re: quality vs quantity of life. It doesn't make much sense to continue chemo and feel very ill all the time. However, your Dad should not have to be in pain; there are multiple meds available to take care of this issue. He or perhaps you should speak to his oncologist about the pain issue.
Ultimately, final decisions about your Dad's treatment are up to him. Whatever he decides to do, it is up to you to support and love him even if not in agreement.
Good luck and God speed.
Joan L
P. S. There is a lot of knowlege and support to be had on the Hopkins board. Drop in and see.