If you're sticking with the stock forward bolt I'd get the improved BMW OEM bolt.
https://www.ecstuning.com/b-genuine-...t/33176760337/
Also if you are considering poly bushings and adjustable lower control arms now would be the time to do it. The Diff has to be slid back 2-3 inches and the axles disconnected to remove the upper and lower inboard control arm bolts.
I just reread the last post. "The crazy thing is when I was turning the bolt I thought I saw the opposite end of the bolt turning too". --- Yes broken bolt can be extracted from the rear of the bolt hole without removing the diff.
If you have a Dremel and a cut-off wheel, cut a slot in the protruding tip of the bolt. Then use a screwdriver to walk it out the back of the bolt bore.