The OP has revealed to smoking 40 roll-ups a day. That's 48mg yield from a medium thickness hand rolled UK Golden Virginia or Amber Leaf (if we believe the tobacco company machines).
A 48mg yield from 3mg liquid would require vaping a minimum of 16 (sixteen) milliliters a day, possibly an entire 30ml bottle if the yield is 50%.
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What I am seeing here, to be honest, is a two part problem.
1. 14mg at 25w was almost certainly too much nicotine. This coupled with stopping smoking would lead to the symptoms described in the thread.
2. 2mg (or 3mg) is only much use to a 40 a day smoker if he or she is vaping lots of it at quite substantial power levels. It would be gentle to vape (on the head and throat) but less effective as a Nicotine alternative.
I have some 1.5mg liquid. I could vape half the 30ml bottle in one day.
I also have some 24mg liquid. 3ml of the that, and I'm in trouble.
If you feel you need to vape 3mg to feel OK, then that's what you should do.
If you are sticking with 25w on your Kanger, I would suggest at least 3mg, maybe 6mg.
6mg (25w) would be perfect for me, now, after smoking 15 rollies a day and vaping for 3.5 years.
The first few days/weeks are very tough, more so for the heavier smoker.