Froom's Movement of Destiny is the book to read. It presents a historical context for 1888, considering existing ill will regarding the "trinity" controversy as an important factor in the prejudices existing and the personalities conflicting. It also shines some light on EGW's endorsement of the 1888 message. She appreciated Waggoner's emphasis on the all sufficiency of Christ, in the context of arguments about His divinity. Theologically, Waggoner's emphasis in his writings on being "made" righteous rather than being "counted" righteous indicates that he had a somewhat limited understanding of justification by faith. He took as his text Romans 5 which says by the righteousness of one many shall be made righteous. This is a direct contradiction of Luther's theology which held that man remains sinful until translation, even though God considers him righteous because of his faith in Christ, hence the famous "simultaneously righteous and sinful" maxim expressed in his Galatians commentary. Perfectionism also flies in the face of this doctrine and Waggoner was a perfectionist, even though he rejected the IJ doctrine.
Conflict over the nature of Christ often hinges on the meaning of the expression "likeness of sinful flesh." All one need do is read Romans 7. Sinful flesh is that of fallen man which renders it impossible to do the will of God, as Romans 7 describes. Jesus obviously did not have a nature like that. I like what you said about Jesus having a unique nature. That solves a lot of problems. Adam and Eve were "born" perfect and they still sinned, not having any predisposition to so do. We are born sinful and cannot help but sin.
Augustine, when asked about sinlessness, said it is like having faith to move mountains. He never did it, never saw anyone do it, never heard of anyone doing it, but wouldn't say it was impossible.