800 calories a day I guess won't hurt. As long as you don't pass that limit then you'll be good. Its a wonderful snack for a 14 day diet. It tastes good and its good for your budget.
As long as your doctor says it is OK, you are in good hand. Just have constant communication with your doctor always. Yes, the liquid form is better, for faster digestions especially liquids that increase your metabolism. .
Yes smoking really affects the human being in your womb. It not just bad for your health but also for the baby. Take care of you body so that you can take good care of that beautiful being in your womb. Quit from smoking and also from drinking and anything that might harm you and your child.
For the both of you, you should call your doctor right away and set an appointment. It maybe imposed some serious threat that you don't know. As cliche as it sound, prevention is always better than cure.