^ It might help to pick up your appetite, also.
Other than that, you'd have to force yourself to eat better. You have to have proper energy before you get into a full exercise regime. As for quitting smoking, we have a
thread here that might be able to give you some pointers on quitting and not going back. For exercise, we have
this thread on bodyweight exercise, where you might be able to find exercises suitable to your fitness level. There is also
this thread on increasing vitality if exercise is not in your immediate best interest.
If you cannot find what you're looking for in those threads, feel free to post in one of them asking a specific question. In general, smokers have far less of an appetite than non-smokers. My aunt, for example, eats probably two sandwiches and 9-12 cups of coffee a day and whatever we are having for dinner. She eats less than 1000 calories a day and wonders why she has no energy.
You're not very likely to receive many replies here, as there are too many issues to decide what you can do to conquer them all. If you look at each issue separately, you might have a better chance at looking at each one as what it really is.
Good luck with these issues and getting sober, op!