yes it was in Gendo's office, therefore he believes in what it represents.
The whole nerv project was 1) to defend humanity against the angels and 2) the instrumentality project.
the tree of life probably relates to 2). The end goal was for humanity to become one so everyone can be 'happy'. I don't know the details of kabbalah but I imagine it relates to this.
Judaism/Christianity is a deep topic and probably does not directly relate to what evangelion was about. But there does seem to be a connection in terms of judaism/Christianity being about salvation of humanity, filling in that flawed nature we as humans have. which is what the instrumentality project was about.
Anno seems to have a focus on the question of how one solves lifes problems. The evangelion characters egos badly handling their life's difficulties. Religion tries to address this very question, placing importance on ones relationship with God to solve the question of how to live life("God is in his heaven, all is right with the world").
There is the connection that religion is a form of therapy and transformation. Jesus healed the demons that people suffered from. Life is about confronting our demons and living life the best we can. In M scott Peck's book: 'the road less travelled' He brings together God and psychotherapy. It is well worth reading to see the connection with religion(spirituality) and psychological problems, two big themes in evangelion.