Plot hole: When Vlad enters Mehmed's tent, the entire floor is covered in silver coins and Mehmed remarks on Vlad's weakness to it. There's no way that Mehmed could have known about Vlad being a vampire or about his weakness to silver, as Vlad had killed every Turk after becoming a vampire, so nobody would be alive to tell him. Even the Turk found on the battlefield in the morning lived long enough only to deliver Vlad's message, but died immediately after that.
Plot hole: The crux of the plot (one of the many plotlines, that is) is that Harry Osborn hates Spider-man because he refused to help him when he is quickly dying of the same genetic disease that killed his father. You can see the problem in this sentence already; he is a teenager, but he's dying super-quickly (he already has a large ulcer on his neck) of a disease that didn't bother him with severe symptoms before and that took away his father at 63. No reason is given of this sudden outburst in Harry's case, in fact nobody even acknowledges that such a difference exists.
Suggested correction: Genetic factors? Perhaps the disease manifests earlier in Harry than in Norman. Furthermore, what guarantees that Norman didn't exhibit the same symptoms when he was Harry's age? His question about whether he was already experiencing the symptoms strongly implies that he was already manifesting them at the age Harry is now. As for Norman still living for more than six decades, the film establishes that he was a scientist, so he probably could have worked on ways to delay his disease.