Hi,
I have never been diagnosed with pre-diabetes so I can't answer your first question.
Are you eating a low carb diet? Cutting the carbs right down will help your glucose levels a lot, and will also help you lose weight.
It is a very good idea to check your glucose before you eat and again 2 hours after your first bite. This will tell you whether that meal caused your levels to rise too much. If it did (say above 36mg/dl or 2mmol/) then there were too many carbs in that meal that need tweaking and reducing.
Being overweight is a symptom of insulin resistance, although not everyone overweight has insulin resistance, but I suggest that as you are pre-diabetic, you are also likely to have this.