Questions from Domodossola to Brig

We (2 persons and a child) will be visiting Interlaken and the Jungfrau region . We are trying to plan our trip and consider options but we have a few questions regarding the Swiss Card, and Half Fare Card. We would appreciate any clarifications as it would help us to decide how we will travel.

Questions:
1) Can I buy the Swiss Card/Half Fare Card at Milan Malpensa Airport or the Domodossola train station in Italy before going to Interlaken? Will it be more expensive? Any additonal costs?

2) Can I use the Swiss Card/Half Fare Card to buy Swiss tickets at half price at Domodossola train station in Italy, e.g. Domodossola Station,or can I only do so at Swiss stations and at the website?
3) Swiss Card – As the Swiss Card includes the first and last trip from the border to a Swiss destination and back, can I just buy the train ticket only for Milan to Domodossola, and the rest of the journey from Domodossola to Murren would be included in the Swiss Card (journey from the border) so no need to buy tickets?

I am confused when I search a ticket from Domodossola to Brig on Italian train website
http://www.trenitalia.com/. It requires to pay 3.5 Euro for each adult ticket with the option GA Switzerland, which should be equivalent to Swiss Card in this case.

4)If I cannot buy a Swiss Card/HalfFare Card at Domodossola Station and have to buy a full ticket for the Eurocity train to Brig/Spiez, can I buy Swiss Card/HalfFare cards and tickets for the trip from Brig to Spiez on the SBB train?

5) The Swiss card would also give me 50% discount for the cable car rides out from Murren and Wengen, and also the Jungfraujoch and Schilthorn? After I buy SBB train tickets/cards,I will get a Swiss Family Card for my child, is it also free for my child to travel with us on the train to the Jungfraujoch, with the Family Card?

Many thanks!

Hi, Arno:
Thanks for your quick reply.
Yes, I will go to Interlaken from Domodossola on Jun 26 and will head for Chiasso to get back. In this case, I can buy a Swiss Card for this route, right? I have calculated that Swiss Card might be a much more cheaper option for me if I need not pay 4 Euros fee to buy SC in China and 3.5 Euros ticket for the Italian railway at Domodossola.

For Question 3) That's to say that I need not to buy a ticket to Brig before I get on the train at Domodossola with a Swiss Card at hand already? I will arrive at the Domodossola Station by bus from Milan Malpensa Airport directly. Am I right? Italian Railway Website shows a 3.5-Euro ticket from Domodossola to Brig. That indeed confuses me.

If I take the train EC52 or EC54 or IC1080, shall I make any seat reservation when I get on the train at Domodossola?
Your helps are highly appreciated indeed.

On Italian railway website, each ticket from Domo to Brig with GA2 card option will cost 3.5 Euros, which might be a reservation cost. On SBB, it costs about 7 Swiss Franks. Seat reservation is mandatory. I know what to do now.
Many thank to you, Arno!