From talking to people of various churches (and actually listening to them) various churches have various beliefs and various people believe various degrees of what their churches teach, making for enormous diversity of doctrine. To pigeon-hole "Christendom" into a single, narrow belief system is patent misinformation and propaganda. Granted, the Bible makes it clear there are only 2 types of religion to God: True and false. What the JWs fail to understand is that lock-step adherence to their beliefs is also false. Being "closest to the truth" is not the same as being truth.
I have had many people at the doors tell me they believe no human could die for the sins of several billion people and they believe God himself dying for our sins would be a more even exchange. Some have the understanding that the propitiation was for Adam and that "the whole world" benefits from that even exchange, however.
My understanding, from Scripture - not from JWs - is that Jesus is a lesser god to the father. He is "made of the same stuff", so to speak. My understanding of John 1:1 is that Jesus is literally a "chip off the old block" and thus fully capable of understanding the Father, while not being as powerful since he is merely a small piece of the Father. However, Jesus was not his spiritual god self while on Earth. His personality (a carbon copy of God's) was transfered to the womb of Mary, making him totally human but with a perfect mind and figurative "heart".
Most JWs believe, since he was "perfect", Jesus would still be alive, walking around today, if he hadn't been executed. That, of course, is hogwash. Nothing about Adam was changed but his access to the Tree of Life. There are no Trees of Life on earth now, so neither we nor Jesus could partake of them and indefinitely live. According to Revelation, Trees of Life (whatever they may be) will be plentiful in the New World, but even according to the Bible, "perfect" humans are not eternal of themselves.
As far as Adam believing he'd go to Heaven, that's a new one on me. It sounds like he's taking a lot of liberties with the "become like God" aspect of Satan's temptation to Eve and then overlaying it on churches. I've made the connection in my preaching that a form of the idea of not dying, but becoming like God is what most churches teach, but never suggested anyone believed Adam was trying for that.
It sounds like a typical JW (il)logical leap made out of completely misunderstanding everyone else. It may be that in his JW-inflicted ignorance, he believes this or it may be that he understands he can say whatever he wants to because all the other JWs are too ignorant to know any better and won't verify anything he says. I've never heard any other JW say that, but rumor and myth spread like wildfire among JWs, so it may only be a matter of time. In the simplistic, cultish mind of a JW, anything the C/O says comes from Bethel and everything Bethel says comes from the very mind and mouth of God. This being the case, perhaps to many JW retards, this will become doctrine.
As far as Mormon understanding of the whole Garden of Eden thing; they've totally lost their minds. Nearly every part of it is falsified in Scripture, even though they insist their religion doesn't violate the Bible, but merely add to it.