Just because you don't agree with his position doesn't necessarily make him wrong, and to that point, just three weeks ago a second Federal Court judge ruled that the structure of the CFPB is unconstitutional (thus reaffirming Kavanaugh's original point). So this topic will be likely be going to the SCOTUS in the near future (care to take a guess how it will end?).

Kavanaugh is considered to be an expert on separation of powers, and the reason he focused so much on that point was that, if an organization is unconstitutionally structured to begin with, then the other tangential items become moot. After all, the constitutionality of the CFPB was one of the arguments brought before the court as part of that case, and since that was in his wheelhouse he focused on that key element.

Also, you are incorrect that he dissented in trying to declare the ACA unconstitutional. He simply argued that the court didn't have the jurisdiction to hear the case, which technically he had a valid point. The case brought before the court primarily centered around whether the ACA imposed a "penalty" or a "tax." The tax code includes an Anti-Injunction Act (AIA) that says you can't challenge the collection of a tax before the tax is actually enforced. Kavanaugh's basic argument was that, using logic that the penalty was actually a tax, the AIA barred the suit brought before the court. The difference when it got to the Supreme Court was that even though Roberts agreed that the penalty should be considered a tax for determining the fate of the ACA, it couldn't be barred under the AIA because it wasn't technically called a tax in the legislation.