Taking all the quotes that have been presented here, along with the Spinoza you provided, (It's been a long time since I read Spinoza, I focus more of my time on Moral Theories.) I think we can say only one thing for sure: Einstein is the only one could have told us exactly what he meant, and we have no way of knowing if we even happen to stumble upon what he did, in fact, mean.
But what it sounds to me, and this could be completely wrong, is that what Einstein is saying is that IF there is a god, then that god is a combination of all the Natural Laws. That if we finally find the Theory of Everything and combine all the forces we know of into one grand, elegant theory, then we have described the nature of god.
To me, I would consider that equivocation, and a form of Agnosticism. I feel truly in awe when I look up into the night sky, or when I look across a beautiful, natural vista. It sounds like Einstein did as well, and he decided to call that experience divine. That sense of divinity was produced in him by the natural laws of the universe, therefore, the natural laws of the universe are god.
Again, I could be talking out my ass here, and since we can't ask Einstein, we'll never know for sure.