But you can't make any reliable statement about "nicotine addiction" if you're taking all your evidence from tobcco studies , as you are.
The big problem with tobqacco studies is that you can't seperate the nicotine from the other addictive chemicals in tobacco smoke. As medical science has begun to realise (mostly thanks to vaping research ) all these old studies are invalid as nicotine research. Too many comfounding variables. You don't need training in medicine to appreciate that, just a basic grounding in research methodology.
It used to be assumed that "smoking addiction" was synonymous with "nicotine addiction". We now know that it isn't. Or rather, some of us now know that it isn;'t, but all the anti-vqaping p[ropaganda has helped to sustain that spurious equation in many people's minds. You would seem to be a case-in-point, because you're repeatedly using those terms interchangeably.
You might be right in saying that NRT is under-researched, but it certainly doesn't follow that research into smoking gives more reliable answers regarding nicotine addictiion. They don't address nicotine aaddiction at all, All they can tell us is that one or more of the numerous chemicals in tobacco smoke is highly addictive. That the main culprit is nicotine now appears increasingly unlikely.