The dial with numbers on it is your thread tension and should probably be set at 3 or 4 but it varies with the type of thread you're using.
Presser foot pressure is a knob on top of your machine--usually above the presser foot & takeup lever area. Not all machines have a knob to adjust the pressure. Those that don't have to be adjusted manually which is more than you want to try.
Bobbin thread tension is set with the tiny screw on the bobbin case. Tiny little turns make big differences so you may want to mark what it is factory set it now with a marker or fingernail polish before you change it.
My advice for now is to make a small practice sandwich, preferably with the same materials as the real quilt. Change your upper thread tension to 3 and lengthen your stitch length. Spray, pin and/or thread baste your practice sandwich--don't forget to starch the backing first & tape it down taut--and then just play with the upper thread tension & stitch length until you're happy with it. You might also want to try without the walking foot. It's possible that your walking foot is applying too much pressure to the sandwich especially if you don't have an adjustment knob.