I'm not being confrontational, but I have to disagree. The difference is so important that the eternal lives of all of mankind depends on it. "No man gets to heaven but through me", is out of the mouth of the Son of God, the only one worthy to inherit the kingdom, and our planet.
We are discussing whether the religions of Islam and Christianity are devoted to the same God, not whether they are the same religion. Of course they are not.
As for the rest of your post, that's more angels-on-the-head-of-a-pin stuff. It's a HUGE mistake to suppose that you can even UNDERSTAND the teachings of Jesus without great mystical inspiration, and those who have gained that inspiration universally find that the similarities among religions outweigh the differences. All are dealing with realities that cannot be told, and as such, all of their teachings are metaphors. All, without exception. And how can it ever be said that one metaphor is "true" while another is "false"?
God is too big to fit into a little box. He will not fit under your hat. You can, metaphorically, say some things about what he IS. But in order to say what he is NOT, you would have to have more knowledge than is humanly possible.
There is a mystical group within Islam (which tends to this error every bit as much as Christianity) called the Sufis. The Sufis are the source of the story of the blind men and the elephant. That story goes like this, for those who haven't heard it:
Six blind men were curious about the nature of the elephant and found one and examined it to see what it was like.
One man stumbled against the elephant's broad side, and said, "The elephant is like a wall!" Another brushed against a tusk and said, "The elephant is like a spear!" A third grasped the animal's sturdy leg and said, "The elephant is like a tree!" A fourth laid hands on the ear, and said "The elephant is like a fan!" The fifth found himself holding the elephant's tail, and said "The elephant is like a rope!" And the last took hold of the trunk and said, "The elephant is like a snake!"
The blind men angrily began arguing with one another and beating each other with their canes, trying to suppress each other's heretical opinions -- when all of them were only partly right, and all of them wrong.
So it is with religions. There is no such thing as a true religion, because the truth cannot be told; it's beyond human language. The greatest spiritual teachers, including Jesus, have always understood this. That's why Jesus taught so often in parables.
Islam and Christianity are not the same religion, anymore than either of them is the same as Judaism, although all three of these are in the same related family. But when they say they worship the same God, the best approach is to accept this, and not get hung up on minutiae.
I think it is huge mistake to turn our Father into some supreme mystic entity that makes no sense to us little creatures. What would be the point?
He gave us the ability to understand him. Adam and Eve walked with him in the cool of the evening. When he talked they understood. When he sat with Abraham around the camp fire, Abraham understood when God spoke.
God is not an aloof being to big to understand. Why would he put into motion a grand scheme that no one could relate to, or figure out? You'd be surprised how "down to Earth" our Abba is.
Think of him more like a father, and less of a supreme being.
All one needs to do is read the Quran and the Bible to figure out the the God of Abraham and the the God of Islam are two completely different Gods. It is NOT 2 religions/same God. And trying to make them the same is to lose our place at our father's table. And to call Him a liar.
Jesus, not Mohammad, paid for our sins thus clearing the way to an eternal life with God. Don't make getting to know him, out of reach.
Little Child, " Daddy is it true God can see everything I do"?
Dad: "He loves you so much he can't take his eyes off of you".