I’m sure you are right even more than you realize when you say you are learning a great deal through this. Be assured that your sufferings will not be wasted. Many texts tell us this, but 2 Cor. 1 is one that particularly comes to mind. Moreover, I was reading in 2 Cor. 5-6 today, and was reminded how Paul proved himself a faithful minister by undergoing so many terrible ordeals. Your perseverance in your discouraging circumstances likewise proves your own faithfulness to God’s call on your life.
I was also thinking about your struggle with assurance. Two thoughts occurred to me. One, the salvation you hope for is not something you must wrest from God, but is an offer, and offer He has already made—and willingly. In other words, God has offered salvation to you; you do not have to make Him willing to save you. He has already demonstrated that by sending His Son for sinners, and then willingly offering that salvation to you.
Second, no one who came to Christ, no one who wanted Him, was turned away. No matter how unworthy they were and felt (e.g., the woman caught in adultery; Zaccheus), no matter how weak, no matter how undesirable (lepers), no matter what. Jesus has promised that He will cast out none of those who want Him, including ministers (like Peter) who disappointed themselves by not being as strong as they thought they would be.
Further, a bruised reed He will not break off, nor will He put out a smoldering wick (Matt. 12:20). A bruised reed is one stepped on and almost broken, hanging by a thread. A smoldering wick is all smoke and almost no light, only a glowing edge along the top of the wick. As worthless as these may feel and are to others, He will not break them or snuff them out. (Incidentally, Richard Sibbes’ A Bruised Reed might be very sweet to you right now.)