I see what you may call the fundamental differences are not of God, they are man's interpretation of scriptures.
The fundamental foundation of all true Faiths will be Love, Unity, Virtues and Morals. They will all fight the good fight, calling us to change for the better, to serve each other, to Love God, loving all our fellow human sisters and brothers.
That the Faiths appear to differ is because the requirements for the age and peoples that Message was delivered to. These can change from age to age. God Annoints a Messenger, known by a New Name, they bring a new creation, a new heaven and earth, the New Word of God and the Laws.
Our One God, is known by many Names and Attributes, but they are all a reflection of the One God.
This change of mind, this frame of reference immediately sees One God in all Faiths, as we now look for the Good that is of God and see the differences for what they really are, they are our own misconceptions, our own misunderstanding of what God has given us.
Regards Tony