as salam alaikum
some scholars have forbidden smoking tobacco, others have allowed it. Certainly it is not a healthy habit and it is better to focus on other things that are not detrimental for our health. Allah gave most of us a voice that should be improved to recite the Qur'an beautifully and invoke Him, and sound health that is amanah and should be preserved to serve Him at the best of our ability.
As far as coming back home at late hours in the night, it is not a good habit also, and it is haram if it causes losing salat al-Fajr.
With prayers for your success.