For 1 and 2

1. Yes if a flight is booked with a JL flight number it counts as part of your JAL group fly on points.

2. There is an option to chose a spouse status as your gift for reaching Emerald status. If I remember correctly, your spouse would also need to have a JAL credit card, and it is only for members in Japan. But I never carefully studied the option.

3 and 4, I leave to others to comment on.