>life is a gift to be cherished and to throw it away is a sin
>the very world will hate you and you are cursed since birth with sin
>Which is it?
The first one. The second one is what the Cathar heretics believed (as well as other gnostics).
>God created this universe every variable is known to him no matter how small, he knows what we will choose with our free will
There you have the problem of omniscience and free will. If God knows everything, that means everything is set, your choices are chosen and free will is not free (servo arbitrio as opposed to libero arbitrio). Some denominations go this way, and they say you're saved even by pure randomness or predestination (your suffering would then be a sign of you being destined to heaven as a rather sick way to glorify the ones who are chosen to be saved). This ideas, reinforced by faulty readings of Romans 9, stem from profound misconceptions about how creation itself happened and what's the process of creation.
God created man in His own image. That's the very first page of the Bible, when all that has been said about God is that He creates, He's the creator. We have to look to how our own creative processes are if we want a glimpse into the whole Creation. Think of painting, music, writing, cooking or whatever other creative enterprise you want. When you create something, it comes from your mind, you will it into existence, and you know everything there is to know about it. That's why God is omniscient about His creation. But not all creations are equal, some are better than others. What makes a creative product "bad"? It's bad when it's forced, when it doesn't follow certain patterns; it's bad when the author tries to cram certain messages or characteristics into his creation; it's also bad when it follows patterns too closely and it becomes predictable; it's bad when it's not something original, something on it's own accord and is instead just an uninspired copy. An artist has full knowledge of his creation, but he doesn't create as a scientist, systematically determining from the beginning every single characteristic. Instead, he wills it into existence, shaping it but also letting it take it's own form, reinventing it with every new stroke of the brush, with every new word typed in, every new note. The artist has full knowledge of his creation, full control but, at the same time, good creations are not so much made by an artist as they are made through the artist.
God is the creator, and His creations are the most perfect imaginable. That's why we have free will. We are, in a way, God's art, made through His will, free to determine how we are developed.
I've struggled with depressive disorders for about two years and managed to leave them behind about a year ago. I know what it is to stare at the gates of Hell. I did believe in God intellectually, but not with my heart; I couldn't understand his existence emotionally. Structure your life. As a work of art, you probably are the equivalent of a poor imitation of Pollock. Start small, as small as you think you can mange, and then a bit smaller. Grow from there. No-fap is a great place to start, so is loosing some weight (provided you need any of those): both involve not doing something, which tends to be easier than doing it. Give yourself easy, repeatable tasks to follow each day: reading 5 pages of a book (can be the Bible, can be anything), praying (highly recommended), doing one 20 minute lesson of that drawing course you've been putting off forever… whatever. Create an structured environment for yourself too: tidy up your room a bit, make sure to have decent hygiene (many in your estate abandon themselves in that area), have a solid eating schedule and avoid snacking. Slowly but surely, you'll manage to align yourself properly and get closer to God. Your misery probably comes, at least in no small part, from being away from Him.
I also had that impeding need for certainty that you had. I needed something that could anchor me, something I could hold onto. As you get some structure into your life, that need fades away and eventually you're content with just guessing and believing, since you'll never truly know anything. Once your life is structured and more or less put together, it's easier to navigate and reorient yourself. I always thought I needed some great Truth so I could build my life oriented to it, but it turns out I was building a ship, not a house, and ships are easier to re-direct when they're properly build, instead of a collection of logs floating in every direction.
Hope that somehow helps. Sorry if it's too long.