Does Evelyn Salt Stop the Bombs out of Patriotism or for Revenge?

I don't think either of your two reasons apply, but something more in between.

While it is true, that her imprisonment and following rescue by Mike broke her and took her away from Orlov's ideals, it didn't magically make her an American patriot but simply comitted to Mike and maybe realizing what Orlov actually did to her. I think after her old family turned up and destroyed her new family and made her in turn destroy Orlov, she sits in some kind of disillusioned limbo between both of her homelands and past ideals, feeling not much of a connection to any of them. So I don't think she is in any way to call a patriot, neither a Russian nor an American one.

However, I think she still wasn't indifferent to the world and its people in general, as also shown when she tried to not kill anyone apart from the people that killed Mike, having been emotionally "broken" by Mike, even if not politically. She thus still didn't want a nuclear attack to happen, even if "only" for moral and not for political reasons.

So neither do I think she was actually a patriot, not having much dedication to the US or any other country, nor do I think she stopped the bombs out of mere protest against Orlov, but also because you don't need to be a patriot to abhor a nuclear attack. While her final state at the end of the movie is one of a rogue agent without a country, on a quest to find the people who messed up her life, she still adheres to some kind of moral ethics, to which the canceling of a nuclear attack certainly belongs.

This is purely my personal interpretation,

Salt loved her husband so much because

Evelyn Salt is being tortured in a North Korean prison on suspicion of being an American spy. Her boyfriend, arachnologist Mike Krause , generates so much publicity that the CIA is forced to arrange a prisoner exchange, despite the agency's policy against it.

But Orlov kills Mike in front of her. So, she started hunting and killing Russian spies. But it left me wondering why Salt risked her life to stop the Nuclear launch. So, I assumed, whatever it takes, Salt wanted to stop Orlov's plans to avenge her husband's death.

In my opinion, Salt is not an American patriot but wanted to track down and kill the Russian spies for murdering her husband brutally in front of her and she continues to do that during the end of the movie.

She does it both out of revenge for her husband and the morality she developed.

Revenge In the helicopter she tells Peabody that shes wants revenge on the Russian spies because "they took everything from her."

Morality She chooses to stage a ruse instead of killing the Russian president, even before her husband dies. And throughout the movie, she prefers non-lethal force when fighting for its own sake.

Her rescue and Krause's love changes her to both love him and change her moral system generally.