First of all, you can't make any ayahuasca without B. caapi. Harmalas extracted from rue will not make ayahuasca. And many would argue that harmalas extracted from B. caapi will not make ayahuasca either, although will come close to ayahuasca in their effects.
If you decide to extract from rue, be aware that the effects will be different as the alkaloid profile is different. You can, however, come close to caapi's alkaloid profile if you do a harmaline-to-THH zinc reduction. For the purpose of microdosing, rue is fine. However, the THH present in the vine adds a lot to the full-on experience, and I don't know what effect its absence in a microdosing regime would have. In any case, let's not call it ayahuasca please.
By tincture, do you mean an alcoholic solution? As that what a tincture means. I'm not sure what the benefits of a tincture would be over an aqueous/acidic brew (decoction, a.k.a. tea, although it's not technically a tea (=infusion)).
Normal ayahuasca 'tea' will keep in a fridge indefinitely if it's concentrated, so for your tincture to last 4-5 months shouldn't be a problem.
Now, with microdosing, I'm not sure if the addition of a DMT-containing plant will make a difference, as it takes full or nearly-full MAO inhibition for the DMT effects to manifest. It may have some effects, but probably not DMT ones.
As for the general effects of microdosing, it's hard to say. Driving shouldn't be a problem, but it depends on what you mean by a microdose. Of productivity, focus and harmony in the soul, I would think the last one would be the most likely. But then, harmony can lead to better productivity if productivity is desired. Just don't expect it to be stimulating like a microdose of LSD. I think its most notable effect would be as an anti-depressant. You'd be happier and more at peace with everything around you.