I know I am jumping in a little late to this particular discussion...
As far as if all religions believe in the same God, this is my feeling. For Christians, God is God the Father, God the Son (Jesus), and God the Holy Spirit. That does make the definition of God different from other religions, and so to me I can't see how all religions could have the same God. However, I do believe that the God of the Jewish religion is who Christians consider God the Father, so by that it is the same God, though, well, not God in the way that I as a Christian understand Him. Really clarifies things, doesn't it?