Depends, what is your situation?
You can get a meter and eat to keep your BG under 8 at 2 hr after eating http://www.phlaunt.com/diabetes/14045524.php
Low carb for weight loss, insulin resistance to get your BG down, a lot follow a LCHF diet
Yes, it's depends on how advanced your diabetes is and your meter will guide you. Generally low-carbing means below 150gm/day or even less. Use the meter and see how many carbs suits you
You can go as low as you like. I am currently on 60 to 70g a day. Many are lower than that, many are higher. You will only know what is right for you by keeping records of your levels before and 2 hours after you eat. I started at 126g a day (average for that month) but it wasn't working so dropped bit by bit to arrive at my current level, which is about right for me.