I don't feel qualified to answer your questions.
I ran my first operation in a sub-division and had no complaints, although it's nothing short of a miracle that I did not. I incinerated and processed with nitric----albeit a great deal of the time at night, so the fumes weren't too noticeable.
My last operation was conducted in what was a relatively remote location initially, but that soon changed as the area developed rapidly. I incinerated carpets out of doors at first, but towards the end, when I sold the business, incinerating carpets was no longer an option. I had a few strangers stop to inform me that there was smoke coming from the roof of the castle when incinerating wastes. A carpet burning is similar to a tire burning.
My fume hood, which filtered solids, but did nothing with fumes, moved roughly 1,000 cfm. It kept my refining area free of smells, as I was constantly pulling air from outside. Made it tough in the winter, with temperatures well below freezing.
I flew under the radar for the entire duration of my refining experiences. That would be difficult today. There are many regs that will need to be addressed-----so if you intend to conduct a legitimate business, your first stop should be with local authorities, to see what conditions you must satisfy. They, above all, will dictate where you can operate. EPA will be very much a part of what guides your future.
I strongly suggest you research refining and achieve a level of competence before refining for others. Customers are hard to gain and easy to lose, which will happen if you make mistakes.
Needed space is related to the depth of your operation. You could refine that volume in a space no larger than 6' x 12', but if you have support equipment (melting furnace, ball mill, agitation tank, filter press, storage for chemicals and supplies), you may find that you might need much more. I had roughly 700 square feet and was very comfortable.
Harold