I think you‘re right that the bush sleeve has caused that bolt to wear through movement.I have compared both fasteners and reviewed how each fits.
View attachment 188065
The original bolt is shouldered at the top, this shoulder fits totally within the upper flange of the rear lower arm. The thinner section of the bolt fits within the bush center sleeve, which has an internal bore of 12.1mm. 10mm of the threads remain in the bush sleeve. Therefore, the top section of the front lower arm bush can move quite freely against the non-threaded portion of the bolt. Replacing the bolt with the screw, there is much less lateral movement, due to the overall larger diameter of the thread. I'm not actually 100% happy to fit either now! But I'm happier to fit the screw than the bolt due to the lesser free movement of the non-tightened parts. I do wonder if the lesser diameter of the bolt shank and therefore the free movement of the bush sleeve contributed to the bent bolt under whatever stress caused it?