Subohming at 0.5 ohm at 35 to 40 watts depending on what device I'm using. I have a defender 36 watt a aspire sub ohm battery and a kanger k box 70 watt. The latter I keep to about 40 watts. The tanks I'm using are the Arctic and the aspire Atlantis.
I might suggest that you double your nicotine to 36mg/ml.
That should give a satisfying hit and only require two or three pulls to get your "fix".
The daily total nicotine consumption should be reduced. 5ml of 1.8%= 9mg VS 2ml of 3.6% = 7.2mg
It sounds like you have a high tolerance.
Personally, I stay at a nicotine level that allows me to vape as much as I please. It is always in my hand and I vape any time I'm not sleeping. 6mg/ml is my happy spot. (.7Ω at native voltage)
I enjoy nicotine and don't feel it is of much harm...for me, reducing my intake only crosses my mind when I find I have used too much and am a bit "spinny" and nausea sets in.
HTH.
Cheers
I