Yeah,
@rphilly is right. Stall should have been the last thing to do.
Go to the hospital, while Lynos explains things and states that he's their guarantor, seek the people whose sickness is the most grievous and then apply the medicine along with the normal doctors. After it gets proven to work, move on to the other patients. Families whose member miraculously got saved would put in the good word to everyone they meet, much quicker than the asspull cart.
Then go to the city apothecaries and try to strike a deal with them so they can cooperate with posehai. If not for making the medicine together, then maybe just giving them a corner to sell their concoctions.
Only then try to open a stall near a place where many workers gather, like the docks, where medicine for minor wounds/illness would be in high demand for quick application.