Seeker_UK
Feelin' nearly faded as my jeans
If you are correct in this scenario, and Putin pursues the use of high-yield thermobaric (non-nuclear) missiles,
Not sure what you're referring to there. The largest thermobaric weapon Russia has is FOAB (https://en.wikipedia.org/wiki/Father_of_All_Bombs) and that has the explosive equivalent of 44 Tonnes of TNT (or 0.04 kT) and that has to be dropped out of the back of a large aircraft (it weighs 7.1 Tonnes and is 7m long).
As for NATO / NATO member using a nuclear response to a conventional attack on a non NATO member state. I doubt it very much.