A decent cover should be fine. You'll get mould regardless unless you open the doors and let the car air for a good few hours each week, the only way to prevent this permenantly is a dehumidifier or leave the windows open an inch when under cover.
Additionally, rather than moving the car backwards and forwards, I'd turn it around once a week. This will prevent flatspots appearing on your tyres a wrecking them (over inflate the tyre to a higher but safe pressure too! About 40 psi should be fine. Helps prevent the flat spot syndrome!)