Of all the questions you answered ...
I'm not familiar with the thread you are using. I've never FMQ'd with a poly so I have no idea if the type of thread might be your problem. Do you have any other thread available?
Other than that it could be your hand speed is too fast for your machine speed. Either slow your hand speed, or increase your machine speed. Your machine speed should remain a constant but your hand speed should slow down in curves.
Have you practiced FMQ on scrap sandwiches first? Are you familiar and comfortable with it? If not, I can't sress enough how much it helps to make practice sandwiches (same material, batting, needle and thread you are using) and get comfortable first. Don't expect to just jump into FMQ - it takes time. LOTS of time. Sure some are quicker than others, but it will still take many hours before you are even comfortable and uniform.
Good luck.