No, it will hurt your baby less if you quit.
That's an interesting question. I'm not a smoker myself but have had friends in similar situations. They encourage you to stop smoking at the beginning of pregnancy because it can cause developmental issues with the pregnancy - low birth weight, under developed lungs etc. However, I've heard that if you have smoked throughout pregnancy, if you try to stop that the withdrawal symptoms can also cause the baby distress. Have a word with your doctor. It might help to cut down whatever amount you can do comfortably. Good luck!.
The reason they say not to quit all at once is because it will cause you stress which is not good for baby. If you can quit without being stressed then yes it is recommended. But as your so close to birth I don't think it will change much. The main benefit will be that your baby will be getting more blood and oxygen through the umbilical cord. and it would be better to quit before baby arrives so you can get in the habit of not smoking. Good luck
I would talk to your Dr. As above while it's good to quit going cold turkey is not recommended. It may be good for you to form a plan to cut back at safe in travels.