Just because you found something subjectively difficult does not actually mean that there was a problem with an argument.

I have seen students of Calculus insist that the whole thing doesn't make any sense and doesn't prove anything just because they found it difficult.  One of my own students insisted to me that modus tollens was invalid because it didn't make sense to her.

I think the popular conception of how much consensus there is in science and how little consensus there is in philosophy is deeply misleading.  As a matter of fact there are widespread divisions over fundamental questions in science.  GUT has been famously elusive.  On the other hand, there is a lot more consensus in philosophy than might first appear to be the case simply because philosophy typically proceeds by laying out all the views regardless of the real percentages of people who believe them.  For example, I don't know anyone professionally who disagrees with the law of noncontradiction.  David Lewis is famous for being one of a vanishingly small percentage of philosophers willing to embrace modal realism.  I could go on and on.

If we are going with subjective level of certainty as a kind of confidence level, I am more certain that God exists than that electrons really are the way they are described in my physics textbook.

I would echo what Jason and Alexander said.  Love God is the first commandment and love your neighbor is the second.

Ultimately, we are for God as the ground and source of all things.  He is the center of the whole, the ultimate purpose behind all purposes, the Good itself.  So asking, "what is the point of loving God?" is a little like asking "What is the point of the point?"

I will also say that I am highly skeptical of claims that the world is made "a better place" by this or that initiative.  Human beings are very complicated and pushing on one place has unforeseen ramifications in another place.  It may appear at first that it is obvious that the would would be made a better place if we just emphasized "love one another," but I have watched as other teachings which seem to be obviously good have deeply negative consequences.  I suspect that detaching the teaching that we are to love one another from any teaching about a relationship with God, the forgiveness of Christ, the necessity of loving others in a particular way rather than whatever we feel like etc. will actually make the world a worse place.

For example, suppose that I am a pastor who teaches love love love every Sunday and nothing else.  Now suppose that I have a member of my congregation who tries really hard to do this but has various old habits and selfish pieces of his psychology.  Ultimately, he becomes extremely frustrated in his inability to love well.  Has my teaching helped?  I'm doubtful.  In fact, I've been to congregations that do more or less what you are suggesting and I think they were far less loving places than the places I have been that preach orthodox Christianity.

If you want some unsolicited advice, I think the attempt to have a relationship with God on your own is extremely difficult if not impossible.  Seek out the best priest or pastor you can find and become a faithful member of a religious community.  Ongoing relationship with God r

I just wanted to share the news with this wonderful community that I just successfully defended my doctoral dissertation.

It might help to ask your friend, then, what he means by "rationality."  In my experience, most people who hold views like what you describe think of "rationality" simply as thinking or problem solving, which animals clearly do and which easily can be thought to come in degrees.  This is very different than what Aristotelians mean when they say that humans are the only rational animals.  Book I of the Politics is a good place to start where Aristotle compares humans to other gregarious animals that communicate, such as bees.  What humans have that bees don't is not communication but "speech," that is the ability to abstract the λόγος of things, think about them at this higher-order level, and communicate those thoughts to others.  Dogs obviously cannot do this.  Dogs communicate, but they do not signify.

*cough*