As much as the Peace Democrats in the Senate wanted to leave Lincoln "hung out to dry," there was no chance of impeachment. Congress supported Lincoln's conduct of the war, and retrospectively approved all of his actions taken at a time when the fate of the Nation was in the balance. Professor Farber has adequately explained the background to the Habeas Corpus Bill of 1863, sometimes mislabeled the "Indemnity Act," and demonstrated the legality of the congressional action.
Congress, by the way, even during the Civil War, did not meet year round. For instance, in 1863, the entire Congress did not even meet from early March until early December (by their own schedule).
Lincoln governed the Nation much of the time, not in spite of the Congress, but in the absence of Congress.
Gee, you think that the fact there was a little matter of a civil war resulted in Congress's deference to Lincoln and his role as commander and chief?