Scott, I now see the problem...
You may find it will help if you remove the black plastic pushrod/plunger between the back of the pedal and the brake valve... It just pulls out from the back of the pedal and is in two halves with a spring inside... As an aside, it's a common modification to remove the spring and replace it with a length of 15mm copper water pipe. This sharpens up the brake response and gets rid of the slightly spongy feel imparted by the spring...
Removing the pushrod/plunger should allow a little more 'wiggle room' to get a bit more 'swing' on the nuts...
You may find a short 1/4" drive socket and a slim ratchet head or a cranked ring spanner may be better for the job as they will fit into more confined spaces, also, a 1/4" drive socket with a universal joint between it and the ratchet head may help too.
In the past, for such jobs I've had to make up special tools... One such was a special thin socket to undo Xantia cooling fan nuts. I did this by reducing the 'height' of the socket and grinding flats onto the socket so that it would fit tightly into the jaws of a spanner...
Hope that helps a bit, the photos certainly helped me