1. First and second choices are fine; third choice is not.
2. Yes, "killer" would work, too.
3. use "rejects" (singular subject); yes, "act" is also possible.
4. First choices is fine; second choice should only be "go."
5. "make a stand against" or "fight against" -- both work.
6. When Hamlet returns from England, he learns that Ophelia has committed suicide in a state of madness.