Did you also post this on a Facebook group? I saw something very similar. Anyway that machine looks like a Juki. The feeddogs should drop on that model I believe. I have the Brother 1500 and it is similar. It took me a long time to get it to do FMQ. I use a 100 top stitch needle and a thread holder. I’ve not had a problem with tension but there are suggestions to adjust the pressure on the presser foot. I like the Juki open toe foot for FMQ. My thread tension dial
lines up a tiny bit past the middle line on the right side of the dial. The top part of the guide on the pressure dial for the presser foot is at the top of the middle section. Don’t know what color that is on your machine. I never change the stitch length. You can try with the feed dogs at the second from bottom. Sometimes machines like the feed dogs up a little. I put the thread upside down through the first and third of those little holes before your first tension. Mine does t have that tension thing. Does it sew okay with a straight stitch? Try different threads. Keep us posted! Good luck!