If all else fails see if you can find somebody skilled in using an air arc carbon gouge. I saw a really skilled guy blow out a frozen excavator pin of pretty good size and length with one and did not damage the bore at all. It throws sparks and molten material all over the place (I was there as a second set of eyes to watch for sparks and fires.) Whatever you do be sure to support that heavy frame above you if you or anyone else is underneath it.