One packet of yeast is enough to do a 5 gallon batch. I have used multiple packet just to increase the amount of yeast at the begining but it is not required. When the nutrients are added in steps in the primary it allows for a steady supply of food for the yeast to multiply and work at top performance without the off flavors.
Yes you will need a larger primary with all the fruit. I don't get it into a 5 gallon carboy until the bananas have been removed.
When using 71B-1122 yeast with meads, it is not as strong as it would be with a grape, you still need to consider headspace at the begining. The reason for using this yeast is the tropical fruit esters it creates and the reduction of malic acids . It really brings out the strawberries and bananas in the nose. Think of a Riesling.
about 2 to 2.5 lbs of honey will give a nice sparkle.
Guess I'm still too traditional to use the Zork.