1966/'69 A100 Twins Build
1. Cardboard likely just to help insulate the terminals when removing or installing, and provide a small amount comfort from touching steelwork. Clip that arrow points to will support main 12V positive cable from battery box.
2. My best guess for Ballast resistor
3. I really don't get what that is for.
Added to this, there would have been some sort of soft insulation material all around the doghouse....these things get hot when you're cruising around.