And just what more do you expect him to do, with a hostile minority in the committee, a Senate that supports illegal activity on the part of the President, and a hostile media?
Watergate only happened because of the wholesale, “all in” support of the MSM.
I think he has done far more than most Republicans would have. Probably could have been even more effective if he had the support of Boehner.
Given the extent to which this administration has violated the law, lied under oath and exceeded its powers under the Constitution, I would invite you to research the concept of “Inherent Contempt”.