Since the wind goes around the planet quite reliably at about a hundred hours, I propose linking the balloon to a similarly rotating position less than 150,000 klicks up.
Oh... you did.
Well then...
Er...
What about the fart smell?
All of the breathable atmosphere derived from the atmosphere of Venus will have to undergo a number of processes.
Most obviously, we'll need to separate out the carbon dioxide. While there are mechanical systems for this, there are also biological alternatives. We can envision a simple greenhouse, with a very slow introduction of Venus air into the greenhouse environment.
The plants will love it. With ample sunlight, (double what we get at Earth orbit, and eight times what we've been getting in the Asteroid Belt!), the plants will rapidly convert carbon dioxide to plant mass and oxygen. They would not be particularly effective at removing hydrogen sulfide. It might be prudent to filter that out before introducing gases into the greenhouse.
Generally speaking, ordinary chemicals will be effective at separating the H2S, and further treatments with hydrogen peroxide and ozone will also be useful.
Even so, your concern is appropriate. Just because the "air" outside, (which is a big step up from vacuum!), is at Earth temperature and pressure doesn't mean we can relax our vigilance. In addition to our own "sniffers", we'll need oxygen monitors to warn of low oxygen levels before tragedies should occur.
Besides, look at the bright side! Every sulfur atom removed will provide one more molecule of water!