Soooo, are you saying, you got the nut off the rear motor mount bolt, but the bolt is stuck in the motor mount tube? If so, spray liquid wrench, pb blaster, wd40 or whatever in there by the threads, in the middle where the mount tube is splits, etc and try turning the bolt with an impact wrench or breaker bar. Try turning forward and backward til it breaks loose. Worst case, you may need to heat the end of the bolt with a torch.