Questions about death note anime?

Yes, Misa acquired the shinigami eyes twice, once with Rem and once with Ryuk. And yes, as far as I know it is also true that she got Gelus's and then Rem's lifespans when they died. It is implied at the end of the anime that she committed suicide (on her own, not because of a notebook) soon after Light died, so it seems that she didn't get very much time from Gelus and Rem. This would mean that Watari and L collectively didn't have very much time left when they died, which implies that if Rem had not killed them, Light would probably have killed them soon afterwards.