If you don't understand Nero's motivation, you're forgetting what Romulans are; how emotionally volatile and unpredictable they can be. They were designed as polar opposites to the Vulcans. Irrational and Illogical to the core. To quote First Contact, their addition to our universe was done to provide an "unstable element to an already-volatile situation".
You assume he can control Time Travel. He can't. That was an accident. Also, I believe there is a line in the movie where he basically says that he is doing what he is doing so that the Federation never interferes with Romulus again; ergo saving his planet's future. You're also assuming that if he succeeded he wouldn't send a message to the empire that outlines future events.
The Nero/Spock thing made no sense... but really, did any of Nero's actions or feelings make any sense? His world got destroyed and rather than use time travel to prevent disaster he just wants to go around and blow up Federation planets... ridiculous.
You assume he can control Time Travel. He can't. That was an accident. Also, I believe there is a line in the movie where he basically says that he is doing what he is doing so that the Federation never interferes with Romulus again; ergo saving his planet's future. You're also assuming that if he succeeded he wouldn't send a message to the empire that outlines future events.