4a] He wants to continue fasting so that he can give up smoking

4a]
So look at what you are able to do and strive to do it; seek to do naafil acts of worship that are proven in reports from the Prophet (blessings and peace of Allah be upon him), with regard tofasting and other deeds.
With regard to giving up smoking, that is a good thing and we encourage you to go ahead with it; be determined and be firm with yourself concerning it. There is no doubt that fasting will help you to a great extentwith that. Try to keep yourself busy with acts of worship and find a good environment so that you will not be tempted to go back to this bad habit.

And Allah knows best.

:-* key word:- Days on which it is forbidden to fast