That tool does have a thin wall on it. And that is some damage on the tool. Wow. It was hardened. That is for sure.

All I can say is try it again with a new tool or bring it to a bike shop and see if they have better luck.

Heat often helps as well. If things get to the point that you break another tool, dismantle the freewheel so that you can heat up the only inner part of the freewheel without heating up the rest of the freewheel and try it again. Keep cycling the heat until it gives. It will come off.