Even if You do not seem to be the most friendly one when people are trying to help You with the problem here is some further suggestions about 'who is to blame'.
The bolt in the strut bracket does not seem to be the original one. That kind of bracket ususally have a counter sunk screw and threads in one half of the bracet. The screw is secured with loc-tite and no counter nut on the outside. When Your cutlass bearing was changed probably the mechanic removed the bracket instead of pulling the shaft. He may have ruined the orginal screw and treads and replaced the screw with the bolt secure with 2 nuts! This added amount of sst and even change of alloy in the screw may have encreased the speed of corrosion in the bracket itself.
However the bottom line is still that I think the bracket broke, but I have the feeling that either the boatbuilder or Autoprop may be blamed. The above may even explain why Caliber never has had a bracket failure!