2) Itachi also said Sasuke was his spare, that he enjoyed killing his parents, that he was gonna kill him and rape the corpse, etc. Just saying, hard to take anything he said truly into account when it was all padded down as not to damage Sasuke's fragile little mind. Also, how do you know the second didn't have a bloodline limit? His brohter had it, why wouldn't he?
3) I'm not saying that he'd fight him on the spot but a simple "How the fuck do you have a sharingan?" would suffice. To the end he treated Tobi like a servant so it's safe to say he had no idea who he really was
4) Summoned him through a jutsu invented by the Second himself ( I'm assuming since he's older and probably more gifted ), sounds strange that after creating it himself he wouldn't compose some sort of preventive measures so his corpse wouldn't be used in such a manner. Could also be a plot hole, Kishi doesn't think that far ahead >_>