The first reference of a study about "nicotine addiction" I found in the article you linked was talking about cigarette addition, not nicotine addiction. I did not bother to check the rest, as I asked for specific links to REAL evidence, not some fake evidence about cigarettes to "prove" nicotine by itself (i.e. without
tobacco) is addictive, as we all already know cigarettes are addictive, but you were talking about nicotine instead so please try better next time.
I guess to prove it either way, in a scientific
sense, you would either need to identify a population that used nicotine outside of
tobacco regularly over a longish period, or feed it to volunteers. I suspect the latter would be hard to get approved.
There are plenty of people using nicotine. Apart from vapers there are folks who take other tobacco replacement products like lozenges and patches, but those groups are almost all ex-smokers so you couldn't really prove anything from looking at them.
I get the impression that people who vape but have never smoked are few in number and don't vape for very long, though I could be wrong about that. And I never heard of any never-smokers using patches.
The only instance I've ever heard that could be helpful was some experiments I read about that studied the effect of nicotine in delaying Alzheimer's. Supposedly no problems of dependence were found there, but they weren't long term studies.
I have to guess that there really isn't any solid science on the subject. Unless Mr Gottlieb has some secret results showing that Juuling teenagers are unable to quit. And if he had that we would know about it for sure.