I've never heard of a graduate school giving out extra credit. Look I'm sorry that things are spiraling right now, but you need to own your side of things and I haven't seen that done so far. I get the frustration...I excelled academically and hated getting a marginally lower grade. But to get the highest possible score, something really should be "perfect". Instead of looking at it as though there is something wrong to REDUCE your grade, think of it as maybe you had a great paper but not perfect.