Ok, I got it. I used a 4.5" grinder to grind the nub down small enough I could get one of my Craftsman Bolt-Outs on it and I used a pipe wrench on the metal piece riveted to the flywheel to keep it from turning. I tried to use an impact wrench on the bolt out, but it just stripped the thing out instantly. Thankfully, the next size down fit but the impact stripped that one out instantly as well. I used the bolt-out with the impact wrench to machine a bigger shoulder for me to grab on to with the 3rd smaller size and then used a regular wrench. Some hamming and one shaved off knuckle later, the remains of the weight finally backed off.