Ahh - yes. I went through the same thing. IF takes some personal tweaking so I'll share what I did:
First thing in the am: Almond Milk/Spinach/Berry/Protein Powder (yes, I use whey), fish oil shake.
Meal 1: Huge meal at noon/noon:30 usually last night's leftovers in an egg scramble. This includes a huge protein source (steak, roast), veggies, and I will sprinkle some almond slivers or goat cheese on the top.
Meal 2: Huge dinner around 6:30/7pm. Pretty much the same food composite as above.
I also incorporate green tea and water throughout the day. I do not consider portion control but I am mindful of my protein intake.
This is basically all I eat and I'm totally satiated, do not get tired and in fact, I see a spike in energy around 4pm. Mind you, I was the type of person who ate every two hours and would black out if I went more than 4 hours without food. I was hypoglycemic and IF scared the poop out of me at first.
What helped me succeed at IF was not concentrating on the fasting part but finding the right time of day for my meals and eating when I was hungry which is now only 2x's/day. I don't even think about the hours between meals in terms of asking myself if I am fasting long enough. So I generally stay in a fasted state from 7pm to 7am.
Good luck and do what works best for your body.