I use a cover plate to cover my feed dogs, and no foot. I just looked and I do have a foot I've never used that I don't recognize, I wonder if that's what it is?
If you look at a free motion or darning foot you will see it has a spring on the shank. That is to keep the fabric from popping up and down. You can also get free motion needles with a spring on the shank. You need that spring. Go on line and look at what a free motion foot or darning foot looks like and then get one of them. You need it. You are putting too much tension on your needle with out it and that is why it is breaking. The needle hangs up on the uptake and if you have any speed at all the needle is bent and therefor snaps. I recommend Clotilde's catalog or Nancy's notions. They are not that expensive if you have low shank feet, if you have a Bernina you can get an inexpensive adapter for a low shank foot.