Do you have the specs on the 200proof you’re using. they are not all created equal. Used to be all 200 proof was made using nasty drying agents you do not want to add to peoples meds. Now you can find many sources using molecular sieves to pull that last 5%, and those are generally considered safe.
The only claims I’ve seen that Iso was a better solvent with our favourite biomass came from someone who I believe was using 151 rather than 190. although I could not get them to confirm.
As far as Iso removal, I don’t know that you’re achieving a whole lot with your 50ml of ethanol. your second solvent has a lower boiling point than your first, so is not likely to help remove the Iso as much as say adding a little water and boiling that off.
How are you evaping off your solvent. a rice cooker from the thrift-store works well if run outside with good ventilation. they are designed to stop cooking auto-magically when they go above the boiling point of water. which can be helpful if your operator is easily distracted 