I also have the sapphire 830 but dont have a problem with free motion.
I use Coats and Clark good thread and it works just fine.
My top setting is on 5 and I leave the other settings as they are.
Be sure and only use the green bobbins.
It came with a couple of FM feet and they work fine also.
I have found that the thread holder should be horizontal not upright, it puts more tension on the thread and it wants to break. I have used invisable thread and so far it works fine. breaks once in a while.
Sometimes I adjust the stitch length just to see if it makes it easier but it dosnt seem to make any difference.
And of course set the feed dogs in the down position.
Make sure to clean out the bobbin case regularly it makes a big difference. I use a hand held vacumm it works well.
Sometimes even though I tread the machine right it just wants to be threaded again then works fine.