don't use a seat bolt since the ring terminal will weaken it.

just drill a new hole and bolt to the floor in a location that minimizes the ground wire length. inspect below to ensure you don't hit anything.

removing the seat with the four 14mm nuts and disconnecting the SRS clip is fairly easy.

 

to add to what KHA said. get a wire brush wheel. put it in the drill and go to town on the paint where you are going to ground. dont stop till its shinny.