Hi Suzy,
I am sooo sorry to hear you are still having problems, I can't believe the dealer hasn't been more helpful for you. I had some problems recently with skipped stitches. I tried everything I could think of to no avail. So I called my dealer in Texas and ended up shipping it back there. Turned out they told me I was using the 'new ruler foot' foot from Tin Lizzie and it was causing the skipped stitches due to the needle deflecting. He did alot of adjusting on the tension too and when it came back the top tension is VERY tight but it sure sews like a charm. I thought the top tension was set too tight but evidently not. The bobbin tension is set medium, not too tight and not too loose. I have read that the top tension dial doesn't mean anything as far as settings go, it is just a reference point. I have used Signature thread, King Tut and So Fine in my machine and they all sew great. I haven't tried sewing RA yet, never thought of doing that. And I haven't had a problem with any thread breaking either.
Has your dealer even sent out a technician before? I think I would be emailing the Janome company with some major complaining. I have emailed the tech at Janome a couple of times and he seems very helpful. I will get his address for you if you want. You should have gotten something resolved way before now, and personally, different machines are finicky about their threads, I would try something different than RA thread but would stay with a 40wt cotton. It isn't easy to find, not like you could walk into a store and find it either. The Sewing Studio in Maitland had a couple of Signature cones but I think they are getting rid of that. If the RA obviously isn't working what do you have to loose?
and even though you probably already have have you checked your check spring? If it's hanging up it may be pulling your thread tight and causing it to break. That would be the only place where it would be getting caught. have you taken it off the frame and brought it into your dealer for a once over? If he won't come to you I would be on his door step for sure. Please let me know how you are doing, I really feel for you. Judy