You’re assuming that A, Mueller will find something of significance against Trump, and B, that the IG report will be a plus for Trump. There is no evidence to support either conclusion; both are opinions only.
Bannon called Trump’s firing of Comey the biggest mistake in modern politics. Bannon is supposedly on our side. Anyone who can’t envision the cataclysmic upheaval the firing of Sessions or Mueller would precipitate is not thinking from the POV of the media, the swamp or the entrenched politicians. It would make Watergate look like a picnic.
Actually I've been stating that Mueller's charges will be ~"completely trumped up and based on illegally obtained evidence" but that doesn't mean there won't be a mad rush by many to support them as above reproach. I've also been one of the leading voices suggesting that people should not put their faith in the IG report, since it's coming from the DOJ itself.
Trump is a much better position than Nixon was. First, he's not really guilty of what they're supposed to be investigating him for. Second, he has evidence showing there is likely more crimes committed by the investigators, than by him. Crimes of using government powers against a political opponent, just like Watergate, but in the opposite direction. Third, he has some powerful committees in Congress pointing out the crimes that were performed against him. Fourth, he is seen by his supporters as a transformational figure, and they are emotionally invested in his well being.
A better analogy to Nixon, as far as what they are guilty of, and what is going to happen to them ultimately, is actually probably Comey and Mueller.