Oh my god what is this
Right! For the sake of brevity and those who only need the min I keep things simple. But you’re right – some were located while the rest were lost. Gosh I love seeing all this Tolkien nerdery!
Correct! Gandalf got Narya from Cirdan the Shipwright.
The Doom of Mandos — the Valar of the dead — prevented Celebrimbor and all the Noldor from being able to return to the Undying Lands through his curse, after they turned their back on the gods the first time. To me, Shadow of Mordor definitely seems to be building on this, that he soul cannot find rest because of Mandos’ curse.
You should absolutely read The Silmarillion. Each work barely scratches the surface of what Tolkien created for Arda (his version of the Earth).