well, since your inner fender is gone, hitting it hard with a BF hammer is not an option... I don`t know what tools you have available, but you can probably cut the bolt ( on 2 sides) with a hacksaw ,but that might be a bumpy ride due to lack of space... I would say heat is the way to go... you will need a cuttingtorch for that job since you cant reach the bushing that`s rusted to the bolt.