UPDATE!
SO after reading countless threads on here regarding technique for removing roof rivets, here is my feedback.
1. Regular angle grinder grinding disc or cutting disc. Nope, takes too long
2. Air hammer with chisel bit: Waste of time, too much physical exertion, about 30 seconds/rivet head
3. Flappy paddle disc for angle grinder: HOLY LORD ALMIGHTY THE EASIEST WAY POSSIBLE!
Perhaps 5 seconds a rivet head. Didnt take long to cover the windows to avoid any flecks hitting the glass. Thank you the Slidewayz for the recommendation. By far the easiest/fastest method.
So here is my bare roof. No leaks!!!!!! and Hardly any tar either. Winning
I did start into one wall before I gave up for the day and there is a LOT of tar for the insulation to adhere to. The plan is to spray foam these areas. Should I bother removing the tar? Or can I just spray foam over it?