The state sets the minimums, the county can't set a limit below that but they can allow for larger limits.
Some counties can ban outdoor cultivation but they can't outright ban cultivation. Hope that answers your question.
completely depends on how long you veg them for. In general a plant doubles in size when flowered. 20 plants could fit in the same space as 1 plant, depending on how long / large they are.
bad idea, although hydro shops aren't generally harassed in CA. This is a federal issue, hydroponics has other legal uses besides cultivating mmj, thats their defense. Add a bong and now theres very little defense.
Tell him to stop. Not sure what your business is but this could be a huge insurance / liability hazard. As my boss once told me, leave it at home and keep work at work.