1993 BMW 318 Rear trailing arm

I am trying to remove the trailing arm between the centre of the vehicle to the lower part of the hub area of the rear wheel. It somehow got badly bent, likely being towed out of a driveway last winter. I am not sure if the bolt in the centre of the car is is a nut and bolt or just a bolt, and it is very difficult to get at since the rear differential is only about an inch and a half behind it. Any suggestions on how to remove it would be appreciated! I was planning on heating the the bolt, but do not want to damage any bushings where this 'subframe' that goes up and around the differential. Thanks for your help!