You can mix and match any components you want. Why they sold such a big pump? They made more $$$ and they could have been stupid. In my opinion there is no magic number for the number of water turnovers in a day. I'd say run it as little as necessary to keep the water clean and sanitized, read...keeping the chlorine mixed well. Trial and error is your best option. Again, in my opinion...others have different thoughts and advice.
Al