Try that link again - I've edited it to correct it.
Fasting is indeed a difficult one. For that reason, I oped for dasatinib over nilotinib since they are otherwise roughly as effective as each other. There's no particular reason you could not switch from one to the other at any time, but your doctor might not be massively willing only 9 months in. Perhaps when you achieve MR4 (0.01%) it might be a good time to discuss it, and the impact that nilotinib has on your quality of life.
You won't find much official guidance on when you can reduce dose - most studies (exception being DESTINY) focused on stopping treatment, not reducing it. There is more ongoing work in this area though, but before then you need a doctor who is willing to make educated decisions about when is a reasonable time to reduce dose. It also depends on your aim - if you want to be treatment free one day, the data suggests being on treatment for 5-7 years is probably the thing to do before attempting it.