Jimmy wants to be a good guy, but he is also fascinating by evil and he is very weak against it so... I don't know. A very complicated situation.
Just saw the last scene a second time.
It's like he is... celebrating. He won. He won the struggle to death against his brother.
Love and hate and everything in between.
But in the final scene, looks like he moves forward, he doesn't want to deal with his emotions, put them in a very deep box in his brain, and whistle. But I agree with you Gruic, looks like he won (he may believe this business with insurances is involved)