A proper version of this text would be the following.
"The reporter failed to notice the discrepancies in the report that the congressmen had presented because him and his staff successfully diverted the media's attention to other issues"
Explanation:
The use of the past perfect indicates a past action which happened before another past action. In this way, it helps us organize the different events that took place. First, the congressmen presented the report, later on, the reporter failed to notice the discrepancies in it. On the other hand, "him" is the subject of the sentence and "his" in "his staff" is a possesive pronoun. In this case, the subject must always go in the first place and the possesive pronoun in the second place.
