1. It wont happen. Haniya and Gab are the stable relationship in starmaker, it wont have a steal route.
2. There wont be animations, as stated before is: current version amount of content vs 2-3 animations.
3. A gallery for non repeatable scenes is being thought out for after the game is fully completed, but is not a guarantee to happen.
4. Other might be able to join the basement later, but this will be after a specific quest for the character to join, and no, it wont be most of the girls.
6/7. There will be content with them in the future.