For paragraph II: what I view interesting is the parallel between how Rin died and how Sasuke was about to kill Sakura. I mean, the Sakura gets stabbed with chidori/the Kakashi version of it already almost happened, no? Would Kishi almost do it again? Naruto saw it, too, and his reaction was, well, very mild. Obito went wild with rage seeing Rin stabbed. Naruto witnessed his love almost being killed and reacted with... confessing his undying love to Sakura's almost killer? Granted there is a big difference with being stabbed to death and being saved at the last minute. If you want parallel with Obito going nuts with rage and grief, the closer event is Naruto going kyuubi when Hinata is hurt in the Pain arc, IMO.
Edit. I add: Sakura is parallel to Rin, I know. But Sakura being hurt has never made Naruto lose his temper the way Hinata has. What you seem to be suggesting is that she will eventually be hurt and Naruto will finally react to her death this way. What I'm pointing out is that this scenario, important person being hurt and Naruto going nuts about it, has already happened, and in a major way.
We'll never truly know how Naruto would react in the event of Sakura's death until he believes it has happened. As you said there's a big different between almost happening and actually happening.
It wouldn't be about making Naruto hate Obito for killing her and casing him to explode with anger like it was with Hinata, it's about making Naruto loose hope all together. How about instead of going crazy Naruto simply shuts down, he starts saying that what he's witnessing isn't real, and at the moment Obito tempts him with the moon's eye plan. There Naruto cements himself as different from Obito by refusing.