How detrimental or addictive can smoking be if you take in the smoke into your mouth and exhale without taking it into your lungs?

It still can be both: Addicting and destructive. Nicotine is also absorbed through the mucous membranes of the mouth (this is why people get hooked on chewing tobacco and snuff), and the smoke causes head and neck cancer - cancer of the mouth, tongue, and larynx. In addition, it is highly likely that you will begin to inhale the cigarettes at some point. It is likely you could quit with less trouble than most people.