Loving you is like breathing, how can I stop?
He asked how I had failed in the examination.
In example 1, firstly, there is a comma before the second clause. Secondly, it's in interrogative order. Thirdly, it has a question mark in the end. Furthermore, in the first clause, ( loving is like breathing.) an assertion has been made. While the second clause (How can I stop?) seems more like exclamatory than interrogative, shouldn't it be like, how I can stop!
Now, if we analyse the second sentence, it is devoid of all the three rules. What is the basic difference and what is the role of the word (how) in both of these examples?