Hi! Someone who's been here longer than me, and has gone FMQ on a slant with a Horizontal bobbin will likely chip in, but I've been told that this is one of the most difficult machines to do what you're trying to do on it. It's an excellent machine for almost everything. Everything but FMQ.
The balls underneath are an upper tension problem. Make sure you're threaded right, the thread is tight in between the discs (all the way in...) if it's still not great, try tightening up the tension discs a little more and see what the result is.
Skipping stitches can be from moving too fast. I had the same problem this evening when I was playing with the chain stitcher on my machine. It would skip if I moved too fast, or turned too sharp it seemed.
Other than that, I'm sure someone may have tips for working with that machine for FMQ. I'm still not coordinated enough to stitch straight, nevermind FMQ.
Hope something here helps...