Firstly good on you for posting this, rather than keeping it all bottled up inside.. I can tell from your post you are a very intelligent articulate person.
Secondly do you smoke weed? cos that stuff sometimes distorts views, even though sometimes you think it does help. I have been down this path personally myself.
It is a cruel world out there and it seems to me that you are asking yourself some pretty deep questions. Life isn't always fair and it doesn't always make sense, some people turn to religion to answer some of these deep questions, while others like myself and by the sounds of it you included, have to form our own views, which inherently can be the harder path to walk. Alot of people go through life oblivious and never ask such deep questions - the fact that you have shows you are intelligent person and I have faith that you will get through this hard time.
existential depression can be hard to deal with, have you considered talking to a councilor trained in dealing with people going through this?
other things I suggest is exercise 30 mins a day of jogging or being active released endorphins in the brain which can give you a natural lift. You like to read? you could read books such as "The road less traveled" which tries to answer some of these hard questions. Also another good book which deals almost specifically with esistential depression is the "The Van Gogh Blues: The Creative Person's Path Through Depression" I got a fair bit out of this book.
You are not alone.
Taking comfort in people who have been through depression. Alot of very intelligent famous people have suffered depression. Abraham Lincoln, Winston Churchill and many more, below is a link i found at least a little comforting... find someone who you relate to, and research them! interesting to see how they battled with it.
http://www.geocities.com/coverbridge2k/ ... ssion.html
Be kind to yourself, you are going through a hard time its disappointing your father isn't overly supportive of you, support is very important and its sad to hear you haven't any friends or girlfriend even that you can turn to. Have a look in your area for what support can be offered for depression.. you can join a support group. I joined a depression support network, a good way to share your pain with life amongst others. A problem shared is a problem halved.
I myself was in a similar situation. through my depression I lost an awesome well paying job and a gorgeous girlfriend of 6 years almost simultaneously - was a double blow. I was very sick with depression for 6 months hardly even getting out of bed - let alone leaving the house. Unfortunately my mum who was supposed to be helping me kicked me out at the lowest of low times - she thought i was being lazy. I was forced into a either sink or swim situation.
I am since working again and have been for over a year now. I do still battle this black dog, I have learnt to tame him. His bite isn't as strong and sometimes - SOMETIMES even.. he's in his kennel.
All the best and I will leave you with a positive quote from Sir Winston Churchill...
"If you find yourself going through hell, keep going. I wish you all the peace and consistency in life that we all deserve" - Winston Churchill