What you’re describing is still 12:12, but stricter about not eating between meals. It will probably help you cut calories, but it really won’t give you the health benefits of 16:8 IF. Those come when you fast for 16 consecutive hours. It takes several hours (like 6) for your body to get back into the “fasting” state after a meal — meaning insulin drops back down to baseline. So the 4-hour window between meals wouldn’t really count as “fasting” for those purposes.
I obviously don’t know all the constraints of your schedule. But I did want to note that working out while fasting is an option that you could consider, if it works for your body. I know sometimes people assume they have to eat protein right after a workout in order to build muscle, but that’s really a myth — as long as you get enough protein at some point during the day, your body will use it to build muscle when you work out.
You might find that the longer fast of 16 or 18 hrs in one fasting window reduces your hunger. It definitely did for me.
The headaches are not uncommon in the beginning. Drink enough, but not too much, watch electrolytes, and take it slow to get to 16 and then 18 hrs.