Hi, Lana. I am very sad to hear about your father. My thoughts and prayers are with you all.
I think everyone on this board can relate with how frustrating and scary this cancer can be. (not to mention expensive!) Chemo is only effective at holding the tumors at bay for so long. Eventually, the tumor will build up resistance to the chemo, and the tumors will begin to grow again. It sounds like this is the course that your dad's tumors ran while undergoing treatment at Mayo, although I only speak generally, and am certainly not a doctor.
I think everyone on here will encourage you to seek second, third, fourth opinions. The reality is that cholangiocarcinoma is a specialized cancer, which encourages treatment by specialists. Unfortunately, despite much work, all the brilliant minds have not yet been able to find a solution for cholangiocarcinoma, outside of surgery. Therefore, if your dad is not a surgical candidate, he's ultimately selecting his own treatment based on doctors' recommendations. This requires that he seek as many opinions as possible, and do as much research as possible. There is no right/wrong answer here. If you check around on the boards, you'll find that all the patients on here have very different experiences for similar treatments. Therefore, no one on here can give you a clear direction, although many can give you a good idea of what you may expect with a given treatment.
Personally, I'm very intrigued by some of the success at managing the cancer growth and symptoms through diet. But that's just me. You and your family may pick up on something else entirely through speaking with doctors, doing research, and reading the posts on here. I wish you well on this journey, and please don't hesitate to ask questions on this forum. There are some very knowledgable and helpful people on here - they will answer whenever possible.