Congratulations! Persistence usually pays off and the struggles we go through are part of the learning experience that makes similar jobs easier next time.

FWIW and for othersfollowing along, one of the techniques I use for removing stubborn broken bolts is to drill the broken piece the tap drill size (minor thread diameter) and carefully using a small chisel I will tap on the exposed OD and fold the thin wall into itself until it release from the threaded bore. A needle nose vice grip can then "worry" it loose. That method will also work for a hollow or solid dowel (or bushing) by using a drill as close to the OD of the dowel as possible -- the trick is to get the drill exactly in the center of the bolt or dowel. The most common mistake is not getting it centered and drilling into the bore and damaging the hole. Drilling the part to a thin wall will significantly reduce the grip on the bore and the thin wall makes folding it inward easy and reduces the grip to nothing.

Good job John.