I second what the others posted.. the band does help. The idea is it pulls the tibia back from the restriction and allows you to stretch the front of angle (i doubt this - i think its neural but who cares - it works!).
I recommend the following. Test your dorsiflexion on both legs. I suffer from this problem a lot. Short tibias, flat feet, long femurs, basically worse build for squatting... when i do this i am about 5" and 6" on left and right. Then foam roll, massage, and stretch the hell out of your calves/achilles. Doing this gives me closer to 5.5" and 6.5" which suggests my poor left is not just from calves and achilles but from front of ankle... Not surprisingly the resistance band technique helps my left far more than my right and gets me up to about 6" and 6.75"...
Two other things. Buy an adjustable slant board. Also as far as helping you in squats, realize that if you squat well through the forefoot (not purely heels) the weight of the bar will help, so you will actually get more out of that than the wall test... also dynamically your calf flexibility will increase rom a lot... but yes. Slant board. Great tool.