First of all, you should not be discouraged because FMQ is not really something you can master in just a few days. It takes practice & a lot more practice, so do not continue to beat yourself up. Now, pick one technique and practice it... a lot! Stippling, for example, is a bit easy to get bored with, but it is a great starting point. Sew fast (sort of) & move slow. Since you have 6 king sized quilts to finish, I would recommend putting the walking foot on your machine, & do all of your ditch quilting to all of them first. Then come back to the FMQ on each. In the mean time you can practice the FMQ as you have time, & not feel so overwhelmed by the size of the project as a whole. You can do it, just relax a bit. When you get frustrated, walk away from it for a few minutes.
As for the back thread problem, make sure your stitch legnth is set at 0 and your bobbin is wound correctly. Check your top tension; I find it usually has to be a bit higher when FMQ than when doing standard sewing. Last, but not least, use good thread. Thread causes more problems than you could ever imagine.