Hang in there. I fought for years with free motion quilting. This past summer something finally clicked in my mind and I now can't do enough of it. Mastering machine quilting had been my biggest challenge in the quilting journey. Sometimes whether we realize it or not we have to be mentally ready for a new challenge.
Another marking suggestion that I make use of when I want a specific design is to lay a piece of Glad Press and Seal on the design, trace with a child's markable washer and then press onto the quilt. I have never had a great problem removing the Press and Seal when the design is quilted. Sure beats any type of paper I have ever tried.
I also find that when encountering problems it is best to walk away and then try again. All my work goes more smoothly since I started to seriously stick to the 50 minutes on, 10 minutes off rule. The ten minutes off is for drinking water, bathroom break, either doing stretches or taking a brisk five minute walk, even on the spot. It just clears my head and everything looks better.