I'll admit I don't know much, but I do know this: your final sketch is really good. Relatively clean lines, and neat shape language & simplification with the crab design. I also struggle with getting a drawing just the way I want it. There is a part of the "drawing basics" course that focuses on perspective, in case that helps. I presume you have that course already. Oh, and if you ask me, your lines aren't too wonky. I enjoyed viewing your drawings!