Hi Sunny, Your question is a very good one and i am having a hard time explaining why we say He is the better for it instead of He is better for it. Using the seems to make the statement a little more emphatic: America is the better for having Pres. Obama in the White House. Although, America is better for ... seems to express just about the sa
To me this is the same use of 'the better for' as your first sentence. I don't think 'better' or 'the better' is a pronoun. What would its antecedent be? What would it refer to?
Maybe it is for the better if we just consider it to be an idiomatic phrase of obscure origin.