Hello AlexJaeger
Q1.
The Swiss Half Fare Card enables you to purchase Supersaver tickets at half fare (50% off). Bear in mind that they are tied to the connection you are going to choose during purchase. They do not offer any flexibility, and you have to take the train back at the time indicated on the ticket. A Saver Day Pass would give you more flexibility as it is valid on any train.
Q2.
Each passenger needs their own Swiss Half Fare Card. They are personalised and only the person holding the SHFC is eligible for half fare tickets.
Q3.
The Swiss Half Fare Card is not a ticket. It simply allows you to purchase tickets at a reduced cost. It can be used with any ticket type.
It is challenging to give you correct advice as we neither know how long you are going to stay, nor your age. Perhaps a Day Pass Friends could be a viable option if you are age is below 25 years. Also, any train that goes above Wengen / Grindelwald is not covered by the tickets we mentioned above, you would need additional tickets for the mountain railways, gondolas, and cable cars.
If you want us to give further advice, you have to tell us more about yourself and the length of your trip.
Kind regards,
Roland