Banded serpent star emergency!

I was going about my daily afternoon feeding when I noticed that my banded brittle didn't eat the 1/2 silverside that I offer him occasionally (once a week). I also noticed that he was hiding on the opposite side of the tank (he has a favorite place to hide) and my fish were picking at him. So I decided to take a look under the rock.



The top of the star's disc is gone. I can see the inside-bottom of his disc. All of his stomach is gone. I don't know how but he's still alive (I moved his legs).



30g hex tank. Last w/c 12/19/14. I just took parameters.

NO3 - 10

NO2 - 0

NH - 0

pH - 7.8 I'm almost positive this is the problem. It was 8.1 before the water change. I don't have anymore buffer!

PO4 - 0.3

Ca2 - 360

KH - 11

SG - my refractometer is broken, also the problem

Temp - 80



Should I remove him from the tank...? I don't know if I'll be able to... Everything I've read on WWM says that once the central disc starts to disintegrate, they're goners. A hopeful post elsewhere said they can recover from this, but he's not eating or moving very much... he grabbed the silverside I gave him but decided to let it go. The hole is probably quarter sized... I feel so stupid for not checking the NSW parameters before doing the water change, I guess I've learned my lesson... :(



Kris