It really appears this boy has no idea who he is yet. One does not change for another person, nor do we try to change the other person.
Agree, drinking, playing video games all the time is often non productive but it is what young boys do, until they find a purpose in life. Life is goals, and making the most out of it, for you.
This person has changed who he is, no wonder he is confused. Now he thinks, the girl should change because he did. It does not work like that. The girl was wrong, in trying to make you into someone else. (even if that someone is a better person)
You on the same issue, have no right what so ever, to make demands on her to change, You may discuss your wishes, but not dwell on them. Once said, if she does not wish to change, she has no right to.
You seem obsessed with religion, although you seem to be the only one really wanting to talk about it.
There are many arguments for God's existence The Ontological arguments of people like Charles Hartshorne, or the classical Cosmological arguments of Plato and Aristotle which were developed by Thomas Aquinas. My favorite is the Teleological arguments, which is often called the argument from design. While developed in ancient Greece (not for a christian god, but a god in general) is best known from the works of David Hume's "Dialogues Concerning natural Religion"
Pure reason, of nature, and the design shows some intelligence for the balance of all things, pure chance seems a much less probable idea.
Religion is a creation of society, but the desire to look and find a god appears to be a natural part of the spirit of man. The idea of denying any level of god, appears to be more from a new nature of man wanting to be the master of all and supreme above anything else.