I'm so sorry. I've been there, not for as long as you have though. I felt like a canyon had opened up in my heart, I walked like a zombie through church, hearing the same words I had heard before but just letting them all drop into the giant crevice.
I am happy to report, though, that, through counselling and a good bishop and sheer force of mind, that rift healed over. It did not disappear. I keep the scar hidden, but I know I will have to show it to others some day who also struggled. I accepted the idea of having a shelf to put my questions on. I found answers or at least balm, little by little, which was most certainly extended to me in answer to sweet prayers uttered on my behalf by loving family members, and maybe a little in response to my own strangled prayers. Most importantly, I stomped down on feelings of guilt about certain choices I had made and refused to ever let them spring up again. I go to church and, the much more effective spiritual act for me, I go to the temple. That is my point of rest.
I wish you the best. I don't have anything to say like "Keep trying" or "Have you tried this or read that?" It sounds like you are thoughtful through it all. I hope you feel the love of your Heavenly parents. I have to believe they listen and watch intently. Again, best of luck, and life, and thought. And peace.
One of the most miraculous proofs of the atonement, to me, is the complete erasure of the memory of the pain I felt at that low point. I know I was miserable, I never want to go there again, and Heavenly Father has given me the gift of being UNABLE to go there again. I literally can't remember that pain anymore. Once, I heard a Relief Society president relate almost exactly the same experience, only she was referring to the pain of being single (she was giving her last lesson before getting married. She was 29). Maybe we all reach these low points. Hopefully we all get delete keys pressed for us by a higher power.
I'm so thankful for the sweet gift of deletion. I plan to show that thanks by looking people in the eyes and helping them in their points of pain, if they will let me.