Modal verbs in past narration

I’m correcting a text that is narrated in the past tense and has many sentences like the following:
Bob realized he’d been lied to; he shouldn’t be so naïve. He could go back and get revenge, it would be easy.

Am I correct in thinking that these should be replaced with "shouldn’t have been", "could have gone", and "would have been"?
Does it matter if some of these verbs represent actions or states that are valid over an extended period of time in the past?