The big missing thing is fresh or dried herb? Fresh herbs have so much water in them, that it dilutes the alcohol percentage, so you want to use more alcohol in the menstrum. I find that in general, using everclear with fresh herbs yields better medicine, for this reason. With dried herbs, vodka works better, because much of the water in the vodka goes to rehydrating the dried herb. Of course, YMMV.
What was the source for your numbers, just curious?
I do not remember the source. I think I got it from Doc Jones.
Based on the percentages listed I would believe that it is for dry herbs, primarily.
One thing you can do is alter the RATIO of herb to menstruum.
While 190 proof is preferred, lower percentages will get the job done. The goal is to have a percentage of alcohol that is AT LEAST 30% to preserve the tincture. Starting with 50% might be best. While maybe not the BEST or most EFFICIENT menstruum, it would get the job done sufficiently.
Like Doc says: Don't make it complicated. People have been doing this for hundreds, if not thousands or years. Science just gets in the way some times.
My go-to for numbers like these is always the wonderful Michael Moore, here is his Materia Medica. There are tons of valuable and free texts available on his website...I could get lost in there for hours and days!
As for fresh vs dry, I've always understood the numbers given to be the percentage of alcohol that you have at the end of the tincturing process. That means that you need to take into account the amount of water in the plants when you are doing fresh tincturing (with dry herbs, the alcohol percentage you start with should be the same you end up with). That's why so many people use everclear for their fresh tinctures - because the water in the plants is going to lower the final proof of your tinctures. There are ways you can mitigate this if you don't have everclear on hand, mostly by letting the plant material wilt for a day or so before tincturing, to remove some of the water.
All that being said, I think Steven is right. As long as you end up with something that has at least 30% alcohol in it, it will be shelf stable, and you are going to get a lot of the good medicine from the herb even without a perfect alcohol percentage.