I'm running VCCSA at 1.80V and PCH at 0.91V for a whole day now, if it boots it should be stable. Did not see the effect of VCCSA as you are describing, my vcore stays the same.
Now testing CPU PLL at 1.5125V, didn't boot at 1.50V, I think it's the same as other two, if it boots, you're OK, but will see how it holds.
Too low VCCIO on other hand, it just shuts down, didn't work on 0.95V, 1.05V is default, so not much headroom left here.

I also saw on previous page a lot of you run Command Rate at 1T, it really works without problem, DDR2 wouldn't run at 1T.