I don't think Crow is the subject of a judicial scene. The title "Examination at the Womb-Door" suggests that Crow is being tested before he can be born. The last line, "Pass, Crow," reveals that Crow has passed the test and is able to pass the gate into birth.
The questions, then, aren't mocking or moral in nature. They are existential. ...
One of the meanings of “furnace” is:
furnace, n. 3. A closed fireplace for heating a building by means of hot-air or hot-water pipes
Oxford English Dictionary.
(This apparatus is more commonly known as a “boiler”.)
So Hughes’ image is of intestines being packed in the abdomen like hot water pipes in a boiler.
I think the most plausible way to make sense of ...