I try to place the tip against the cutting board and raise and lower the middle and rear portion of the blade as I am feeding the scallions through. If you kind of stick your knuckles forward, but never raise the knife above the level of your knuckles, you can keep your fingertips safe. What I still have a lot of trouble with is keeping the blade on one plane while I am doing the chopping. I think I am holding some tension somewhere in my arm.
I reccomend 500 cuts a day. Tell your wife from now on you will do ALL the food preparation because you need the practice.