Hi!
I would recommend to stick to the no eating rule since food, especially fatty foods are known to increase nilotinib plasma concentration. I am using nilotinib as well and trying to comply with the fasting window.
What concerns the 12 hour apart pill taking then this is something where I am a bit more relaxed. Although I take my pills 7 am and 7 pm most of the times, I occasionally have some social events or other things interfering (by interfering I mean I have to eat) which results in taking the pills in example 10 hours or 11 hours apart.
My oncologist has also underlined that fasting is necessary, even if you are otherwise healthy and likely no harm will happen if sometimes fasting is overlooked. But taking medicine less or more than 12 hours apart (+/- a few hours) does not affect treatment results according to her experience.
So, take fasting seriously but don't beat yourself up if occasionally the window between dosing is not 12 hours long. Setting reminders (e.g. a phone app) is a good way to avoid forgetting. I am using MyTherapy.
Be well