No problem. I'm sure I won't have all the answers you are probably looking for, but hopefully I will be able to help with some of them.
I don't know if I understand fully what you are asking here. You might want to clarify some more if I don't address what you are speaking of in the rest of my post.
Yes, but most differences don't change the main message. (things like a Triune God: Father, Son, and Holy Spirit, Salvation, etc.) The Word and overall Message is the same.
Mormons and JW are not considered Christian religions even though they call themselves Christian. As their message is not the same. Catholics are Christians, but different from Protestants in that they believe that their works have something to do with their salvation. Where as Protestants do not believe there is anything we can do in and of ourselves that is worthy enough to deserve the gift/sacrifice Christ made for us. There are other differences of course, but like I said, the main message is the same. Unfortunately, man in his sin and pride, separates the 'body of Christ' (the church). We are told not to do this, but we do.
As Christians we are called to fellowship with one another to sharpen one another, to love one another, to help one another, and to be of service to the community. Nothing is perfect under the Sun, but that should not stop us from participating. Life is messy. It is inevitable.
I hope this helps some more.