I like that you've taken the approach of defining "government" before opining on it. Defining terms is standard practice in philosophy. Different parties of a debate or conversation often attach widely divergent meanings to terms and ideas. Not addressing this problem usually leads to confusion and lack of understanding.
I generally agree with your definition of government, that it is an instrument of force, and that the most pressing issue then becomes the question of determining when its use of force is legitimate. As you point out, the essential question is where to draw the line; it is a question of balance. I've been asking myself this very question within various contexts for many years. The older I get and the more I experiences I have with various cultures, the more I believe that there is no definitive line that can be drawn for all societies in perpetuity. The scales will have a different balance point in different times and places. I'm generally a supporter of the type of liberty/governance balance that Mill, Bastiat, and others espoused. But, I also find Jefferson's idea of not shackling subsequent generations with our own governance systems very compelling.
I enjoyed reading this. Keep it coming. Love the quote from Monty Python by the way!