Why would he even make up revelations like that ?
The first question that needs to be asked is "is a God who punishes people for being born Muslim worth worshiping, even if he did exist?"
An argument often used is that if you were born in India you would likely be Hindu; if you were born in America you would likely be a Christian; if you were born in Iran you would be a Muslim; if you were born in Ancient Greece you would believe in Zeus and Poseidon. We inherit religion from our parents and Islam claims to be the "last religion" meaning it is the final word of God. God, of course, is all powerful and omnipotent. So we must then infer, according to Muhammed's words that you quoted, that God is putting MOST people onto the earth in non-Muslim communities in the knowledge that they will "stand before the fire". That doesn't make any sense to even the most irrational minds. Imagine telling your children that they will be punished if they eat apples but then locking them in a room for two weeks with only apples to eat. It is madness
And why would Muhammed make this up? Well, religions seek power and control and have been important in preserving a sense of identity and a sense of community throughout history. The idea of belonging to a nation and saying "I am Iranian" for example is a relatively new concept which was not present in the 7th and 8th centuries and religion was critical in creating any sense of society with order.
But most importantly, humans are innately predisposed to believe and are innately fearful of no knowing. To not know is a difficult concept for most people to grasp and easy answers are much more palatable. Science works o the boundary of what is known and what is unknown. Islam is a complete description leaving no room for investigation, critical inquiry and scientific discovery through experimental approach. As religion provides a complete picture of the "universe" we live in, people must not question this or the whole thing breaks down. Look at the behaviour of Catholics throughout time, a fine example being the imprisonment of Galileo who observed that the moon was not perfectly spherical as the bible suggested and that Jupiter had moons, inferring the imperfection of the "universe" which went against Aristotelian biblical teachings.
Religion says do not question, do not look and do not investigate. Science says, what is actually there rather than relying on an ancient text written by people who were simply scared of the unknown and were trying to describe the world around them.
But there is no reason to feel depressed at departing from your religion. The truth is far more incredible and amazing that any religion has been able to imagine. We now understand how our Universe developed from a fraction of a second after its inception 13.82 + or - 0.05 billion years ago. Our Universe began to expand but initially was being slowed down in its expansion by the force of dark energy (which we are yet to fully understand). For a reason, yet to be understood, dark energy began to increase the expansion of the Universe which, for some reason, is actually accelerating in its expansion. This is lucky as the physics demonstrates that it is not a given that this process should take place and we are lucky that there is a Universe at all!
Furthermore, the beginning of the Universe would only need to have happened slightly differently to produce a Universe incapable of creating the vital ingredients required for life and the elements that make up our world. Lucky!
Adding to that, the odds of our planet Earth being in its exact position in correlation with the sun and the rest of the solar system is ludicrously fortunate. The Moon was essentially a large asteroid that struck our planet, tilting it onto the optimal axis that we now sit versus the Sun. Without this intervention, Earth would be uninhabitable. There are also many variables that have contributed to the fact that life can exist (Jupiter's historical movements, The Sun's strength, the speed and distance or our orbit etc) Basically, this is all highly, highly unlikely and we are stupidly fortunate to be here.
But what about LIFE itself? As far as we know, life has only come into existence once. 4.1 billion years ago, the first microbial life forms emerged that we all share common ancestry and DNA with. We are all related to everything on the planet that is alive. How did this happen, we are not sure but we WILL find out. What is interesting is that life has only emerged once, or so we think, meaning that even on Earth where the conditions for life are apparently "perfect" life has only emerged once and that was highly unlikely.
Adding again to that is the leap from singular cell organisms to multiple cell organisms - highly unlikely. Then the leap from multiple cell organisms to animals, plants - highly unlikely. Then the leap from animals and birds to intelligent life like us - even more unlikely. All of these events are, of course, possible and may have happened on another planet in the Universe given the billions of stars and billions of planets that must orbit them, but they are still extremely unlikely. You would have more chance of winning the lottery a million times in a row (if you could live that long) than for the processes that have taken place for us to be here to be here. AMAZING!
You don't need to have an afterlife to feel there is meaning. We are so fortunate to be hear that we should cherish each moment. I didn't exist for 13.8 billion years, now I do, but soon I won't exist again forever. Doesn't that mean that this incredible fortunate experience is worth treasuring? Doesn't that mean that the purpose for life is to enjoy and ensure that others can also enjoy? Doesn't that mean that by imposing strict rules on people through religion we are essentially wasting their time on trivial matters that ultimately don't matter?
I think that the Universe is so incredible, the unknown is so exciting and the possibility of an infinite Universe so mind boggling that I struggle to not be happy. I hope that you can also come to terms with this and appreciate the wonder of the world you live in. Muhammed didn't have the imagination to invent reality. Reality is magic!
If you want to know more, I would suggest listening to the Infinite Monkey Cage podcasts. They are free and awesome. I use Podcast republic, but I think you can use bbc iplayer radio to listen to them. They talk about loads of topics including science and religion, biology, philosophy and are worth a listen to as they are hilarious and informative.
In 1888, Simon Newcomb that famous astronomer who plotted the pathway of the planets said that we had nothing else to discover with regards to astronomy... So don't worry. The unknown IS knowable