Chris Chicago

Installing a nos deore dx fd last night. I was using a diy shim bc the clamp was 31.8 and the seat tube was 28.6, so I wanted to make sure i got it on tight. after tightening all i could i realized it was too low, started loosening it and the bolt snapped.

2 questions
1)was the bolt just weak or are there other reasons this happens?
2)how do I get the little nut that is somewhat embedded in the derailleur arm out?

thanks!