LZ writes better than many pros. However, your depression seems related to
your inability to see bright side of life and people.
'Life is all about editing.' Try to remember the good and let go of the bad
. You have huge trouble letting go bad memories: you replay them again and
again compulsively. That's why the bad memories become more vavid with time
for you. Same reason that you are writing about them, further committing
them to ink.
Most of us don't have perfect childhood or life but most of us feel better
than you do.
You are in deep depression not because of your parents' bad marriage, nor
your grandparents cold hearts. You are here because you insist on feeling
depressed -- your selective memory and your reflection of the world around
you are distorted. I'm not a medical pro but even I can see it in your
writing.
Find a way out of this please.