Jet,
I just want to add with the others that I too can identify with you, and with the sheer frustration of enduring a seemingly incurable and persistent malady such as depression for so long. And for reaching the point of surrender to self-condemnation.
If you won't take offense, I would like to point out a potential inconsistency in your thinking though. You say that "Whatever God is trying to teach me in this blackness, I am just incapable of grasping".
Oh, really? And yet you follow that statement up with a keen Holy Spirit inspired declaration, "My foundation has collapsed and my hope is gone. The power of the Word feels dead to me."
Why do I suggest that this insight is inspired by the Holy Spirit? Because it agrees with what I consider, imho, to be the most profound revelation of the true source of depression found in Scripture:
Proverbs 12:13 NIV
"Hope deferred makes the heart sick,
but a longing fulfilled is a tree of life."
Friend, you've endured 30 years of deferred hope, but man I tell ya, endured it you have! That isn't faith? And who hasn't attempted suicide, or been strongly tempted toward it? There's a reason you and I failed even at that, because we really didn't want to.
So I advise you to ask yourself, what core longing isn't being fulfilled in your life? I suggest that you've already revealed it, that like me for the 40 years that I suffered crippling depression, I just couldn't measure up to the image I desired for myself - Super Christian.
Do you know how God rescued me from that? By teaching me to die daily to self, including that phantom image I wanted to be in my imagination. To go to His Word in prayer daily, so I could learn who HE really was and who HE says I really am.
Do you know who I am now? A man who is lead by a God who is infinitely patient, able to conquer my sin for me, one who trusts a broken vessel like me to be one of His Ambassadors, and motivates me through ENCOURAGEMENT instead of the whip.
And Jet, that's exactly who you are. You just need to embrace the reality by extending some doggone grace and mercy and compassion towards yourself - it's the only way to pass along the same to others, which happens to be His command, not a suggestion, to all of us Christ-bearers.
One more thing - don't fall for the enemy's lie that all your years of suffering have been for naught. God "turns ashes into garlands" and "restores the years eaten by the locust." I'll leave it to the Spirit to reveal how He does it so that your joy can be full between you and Him!
Daily prayer and Bible study, it's the key to everything else!
Always available to you here or via pm. We are all praying for you and know that you have friends in us. God bless!