Having read all of the above - which is a lot of what I have experienced.
A specialist in the country where I live has made a world first breakthrough in Migraines Headaches etc.
It all starts in the muscles in the shoulders works up to different areas in our head.
Two of you mentioned near the eye area.
You ought to go to a specialist who specialises in Arteries - Vascular Surgeon.
Right next to the eye area where you mentioned that excruciating coin size pain there is an artery and you will more than likely find that particular artery is causing the pain.
This specialist has given thousands of people from all over the world treatment re the areas where you have the horendous pains and they are cured and live now without any migraines/headaches - he changed their lives.
Yes I wasted more money than I wish to remember on my chronic head pains and I finally read about him and saw him on TV here he is the first to have diagnosed my horrific head pains are due to arteries - which he is now working on.
Do not just go to any doctor or specialist go to a specialist who is specialised in arteries.
The Dr I went to has his own headache clinic look it up on the internet and you will get to learn a lot more re your condition. He is now also involved with Harvard University with his first world breakthough.