Another thing I love for FMQ is Little Genie Magic Bobbin washers. They sometimes help with the loops on the back. I love my Supreme slider to help move your quilt around easier. I also like my my Machingers gloves. I have also tried using a throat plate for my Janome with a single hole in it instead of the normal slit that comes with the machine. I have a Janome 9700. The washers and the throat plate have pretty much solved the loops on the back for me.

I also have the 6600 Janome and love it. I have learned though that it performs best when you use bobbins that are specially designed for this machine. These bobbins have grooves set in them and I don't know it that's the secret or if they are just slightly a different size as most plastic bobbins, but I can tell a difference. I obtain these at my local sewing machine shop and also use Organ brand needles. Since I started using both the bobbins and the needles, my FMQ has been much easier without thread breaking and skipped stitches. I also have done many of the things you listed and find that it really helps to keep these things in mind to make the process much easier.

so2sew makes a really good point, it is so important to use the right bobbin, you will never succeed with FMQ with the wrong bobbin.