I'm too tired to do the full legal review, tonight, but I have a number of thoughts having read Barr's "summary". The short answer is that Barr is whitewashing, and trying to fix the playing field before Mueller's actual report hits the street. The wording is too cute, which makes me suspicious. He "quoted" only parts of sentences, and I believe it is going to turn out to have overstated Mueller's conclusions.
For example, he said the report states: "[T]he investigation did not establish that members of the Trump Campaign conspired or coordinated with the Russian government in its election interference activities." Not that he didn't find evidence of it, just that it didn't "establish" it. I suspect he's playing with burdens of proof, here. Not beyond a reasonable doubt, maybe, but to a preponderance of evidence?
More bothersome, to me, is the AG's treatment of the obstruction findings. He declines to prosecute, but because he bootstraps from a collision that the underlying crime wasn't prosecuted. That is NOT the standard for obstruction. This conclusion is mighty suspect, in my view.