A.U.
When we moved to our new house a couple of years ago, our Border Collie became a digger and escape artist. We had priced the invisible fence system, but it was thousands of dollars. We decided to put in an electric fence. If you go to Tractor Supply stores, they can recommend the charge box that will work. Your dog will probably touch wire once, and never do it again. My dog will not even get close if the thing is turned off. I just unplug when my daughter and friends are out. If they do touch, it won't hurt too much. You will have to place wire very low since your dog is tiny, probably nose level. I am not an expert, but the fence works 1oo% of the time for me! A few shocks are safer than him getting out and getting hit by a car.
Blessings, A.