I hate to be one to say it but you may have to drop the diff to get the other bolts out.
I have a removable cover in my boot to get to the diff and brakes but those bolts were still a big pain in the arse. I had to get a ratchet spanner to get them off and it still took an hour.
May be able to remove the handbrake assembly and get to it from under the car but it will be tough.
I'd pull the diff out and do the full vented rear conversion and fix the caliper in one hit.
Good luck, I know first hand that you will need it.
