The smaller blisters that we found are now heat gunned and rolled down. The cracks that we found around a couple of the blisters have been repaired using an acrylic hot tub repair kit matched to my color that my friend recommended. It worked very well, after we used a Dremel to clean up the edges of the cracks and then filled and color coated them. The super huge blister, and a couple others that seemed to be out of the way, we left alone.
We decided it would be very difficult to get the whole blister heated enough to roll it down and we would probably end up causing many cracks in the process. Right now, it looks uncracked and is in a kind of out of the way area where no one's back will probably ever touch it. We shall see, as I still have some repair acrylic left.
I am now working on fixing the rest of the leaks, and have cut off the 6 way manifold, but found it is connected to a T. I would really rather not have to cut out the huge T and cause even more areas for potential leaks later. In the picture below, you can see the remains of the 6 way manifold inside the mouth of the T. Any ideas how to get this bad boy out without damaging the T? I was hoping the T was a pipe and I could cut it back and make a 1 new coupler to extend it, not 6 couplers to extend all 6 small pipes...
