In short: Stimulating a sane and healthy mind is a good idea; my mind (particularly the adaptive unconscious/system 1 part thereof) must now become saner and healthier - then, smoking might work.
I'm now smoking again (I have since just two days or so after posting that), but moderating it - particularly the nicotine intake. At first I simply began smoking less at a time and less often, and keeping track of the state of my mind so as not to fuel the wrong state of mind - smoking only when the 'wrong' pattern of mental activity, to the extent discerned, was absent. Now, I've learned in short order to puff on rather than inhale from my pipe, and so I can easily have a milder smoke - and more than ever enjoy the soft, refreshing "burn" of the pipe tobacco as it clears my mouth and throat.
It seems to me that a small amount of nicotine can still be of use, particularly when mentally working hard. A larger amount still might fuel my overall tendency to burn lots of mental energy producing imaginings and illusions.
Now I'm back to full-fledged smoking. In the course of math studies, the efforts it requires and self-imposed pressure, and reflecting on experiences and Redirecting, and so forth, I've changed the worst of the old mental habits for the better - still more to be done, though. Have got cheap tobacco for making cigars which I grind up and use in my pipe - it is strong enough, and can be inhaled.
More recently, I've again also begun chewing tobacco; while not having the mental sharpening effect of smoking, seems to increase energy and prompt greater awareness of my own memories, helping somewhat over time to "consolidate" my awareness. (The "energy increase" can be ridiculous - when tired, often several times greater than used to be the case years back drinking coffee, but somewhat different. But sometimes it can instead make the mind a bit unfocused and mushy. Perhaps because of stirring things.)
I'm led back to my old thoughts: In cases of autistic spectrum conditions, the brain works a bit differently - according to what I've read, gray matter is denser and white matter less dense in the brain, meaning more efficient local processing but less efficient connectivity across the brain. And nicotine increases (doubles, according to one study) connectivity across the brain. So my thought is that it is likely to be very beneficial for those, like me, on the spectrum. But as I've learned, after a life of wrong diet, as well as plenty of emotional suffering and dissociation, there's a lot of stuff that can work wrong in the brain - and before it gets sorted out, increasing connectivity can increase the noise in the brain and its processing, fuel the work of still-faulty circuits.