I think we are at a point where the President can no longer wash his hands of DOJ lack of prosecution. If Comey et al walk I’m not sure the President will be reelected in 2020. You can put blame on Sessions and Barr and Rosenstein and Wray only for so long. Ultimately all of those people work directly for the President and it’s his responsibility to make sure the laws of the land are followed.
Ultimately, all four of the people you mention are confirmed by the useless US Senate. Recall POTUS floated the idea of removing Sessions and was immediately publicly threatened by GOP Senators not to do that. Recall the GOP Senate recently blocking Trump’s MAGA picks for Fed and DNI.
The GOP uses the coup to hamstring POTUS and stall the MAGA agenda. It couldn’t be more obvious.
Confirmed by the Senate doesn’t change anything. All of these people are chosen by and report directly to the President. He can fire any or all of them at any moment for any reason or no reason. The President is ultimately responsible.