Satan, the deceiver, is deceived himself. His falling away is proof of that. Thus he would not necessarily know the impossibility of Jesus sinning. He may even know it but refuse to believe it, since he is so filled with self-righteousness and unaccepting of the truth.
That is conjecture and you missing some good stuff to your thinking with such an explanation.
Also just to add, Jesus was not tempted as we are tempted, for His temptation was one of external temptation, while ours is one of internal temptation (we are fallen, He was not). Thus His temptation would more appropriately be identified with Adam's.
O Really? Jesus wasn't "tempted in all ways like man yet without sin". Interesting. If He couldn't fail then why the temptation . . . .as man? Are you also saying He didn't hungry, which is proof He had to deal with an internal temptation?
However, your identifying Jesus with Adam is on the right track.
So, why was Adam tempted? Using the same analogy, why did Adam fail and Jesus succeed? In this you gotta keep in mind that all divine attributes of the "Word" were laid side in the life of Jesus. This will help in placing them pretty much on the same playing field.