It sounds to me like you would benefit from getting a Towa guage for your bobbin case. If the tension is not improving when you adjust the top, then you need to get that little screwdriver out and adjust the bobbin, from your photo it looks too tight. Do not be afraid to adjust your bobbin tension. While I prefer to use similar colored threads in both top and bottom, sometimes I simply don't want that and am forced to use highly contrasting threads for the look I want on both front and back.