Ok, poor you! that lighting switch problem is soo common. It causes many owners problems for the dipped beam lights.
It is a well known problem and widely discussed one amongst the owners forums.
I went belt and braces to get around this on my car. I fitted 4 battery fed fuses feeding 4 relays. The relays are located, 2 each in the headlamp pods. This way each bulb filament gets its own 12v switched supply, making my H4 headlights as bright as any. The individual fuse & relay ensures 75% headlights availability should any fault / bulb happen. And, your lighting switch, fuse board and Ign switch all benefit from a huge reduction in running current, in addition your headlights are proper bright and not candles!