I am still playing around with all this myself, but what I am doing (for just my second day today!) is having my BPC to break my fast, about 1:30 for me, I usually eat around 2. I just love my fatty coffee, it is my "treat" now. But it is calories, and if I want to keep my fasting time as effective as possible, it makes sense to put no calories on board - not even pure fat.
And bear in mind I am not a nutrition, diet or health expert! My understanding is that fat metabolism is FAR more efficient. The advice to get up and shove hashbrowns and toast in our face first thing in the morning is REALLY bad - we are in fat burning mode - high energy output - and then we throw carbs on the fire that are like wet wood. Sure, it burns, but it smokes and sputters compared to the fat flame. If you are insulin resistant that would be exaggerated, low quality carbs are like narcotics to me lol! Try Thomas DeLauer on youtube, he is another one I watch a lot and he is more about general fitness. Berg is about STRICT keto for specific health issues. I watch them both, and try to pick the info that applies to my situation best I can.
Let me know how you do with this, I think you are going to be very happy with your health long term.