Well, actually your initial question was quite different

Basically you asked whether a Spinoza \Einstein's God, can make sense also in the light of modern Physics

I am not a religious guy but it would hard to me to beleive in a non personal God
Phanteism is, in my opinion, a synonimous with atheism

Moreover the equation E = M*C^2 does not claim what you ( and many others ) seem to beleive, as far as I can understand from your post

This is a commmon misconception of the equation