Praise be to Allaah.
Praise be to Allaah Who has helped you to give up this haraam thing (smoking). We ask Allaah to make us and you steadfast in adhering to His religion until death.
Your joining Sha'baan and Ramadaan by fasting from one until the other is permissible.
You have followed the Sunnah by doing that. See question no. 13726 and 26850.