I was finally able to get it off!BE VERY CAREFUL!!!!! The right side rear on my car is the one that snapped off on me , nearly flush with the block.
Nothing I tried worked to get it out, including heating the block cherry red in that area several times with my touch, on blaster for days, etc.
I ended up drilling it out and tapping the hole to 3/8 for now. Its holding just fine, but my engine is stock, no slicks, etc.
Total multi week nightmare and I nearly conceded and pulled the engine, but got it tapped straight so that worked. If I didnt have a lift in my shop I dont think I could have gotten it tapped straight as it was very difficult/ limited access to work.
Keep working it as you've been and dont snap it off like I did and spare yourself the pain and aggravation. Good luck.