I do not smoke. (right now)
*This statement can imply both that you don't smoke right now or in general. I do not smoke can be interpreted as 'I don't smoke now, nor have I or will I.'
I cannot smoke. ( I do not want to smoke, because of my health or ...)
*Saying 'I cannot smoke' implies that you can't smoke because of a reason (health, etc) whereas saying 'I don't smoke' can imply either that you don't want to or that you choose not to for a particular reason/reasons.
I cannot not smoke. (I need to smoke - I am addicted to smoking- I can not discard smoking.)
*Very good! Most people have problems with double negatives. Make sure you say 'not' as opposed to 'no'.
I can not smoke. ( I got used to smoking but I am self control too.)
*This is accurate, however you would have to put extra emphasis on *not* when speaking. However, most people wouldn't phrase it this way simply because it can cause confusion. You could say something like, I can choose not to smoke. That implies more self control than the original sentence.