since your reading of .93k at even 125f there is no way that light should come on CO says more like 230ma to glow full so I would guess you need prob a min of 75ma to notice it.
that being the case the thermistor must be getting much hotter that 125f. more on the order of .15k or 150 ohms to flow about 80mA just to get it to light dimly.
So the issue now become if you insert a pot to lower the resistance in an effort to keep the light from coming on, anything more that 150 ohm in series with the thermistor will prob keep it from lighting no matter what the thermistor is doing.
therefore any added resistance should be no more that 150ohms and clearly more than 0 (otherwise it has not benefit). I will dig around my pot stash and look for a 100 ohm WW rheostat. I have some that were used in old color convergence boards for TV's in the vacuum tube era.