Well EC-1118 is a strong yeast and will ferment pretty dry. I wouldn't recommend it if you want to preserve the pear flavor (71B-1122 or Montrachet work much better).
As far as how much will fit in your fermenter... it depends on whether you are going to add then whole or juice them. When I've used pears I get about 1 1/2 - 2 cups juice per pound. If you only use juice and no extra sugar you may use close to all pears.
As yeast goes 1 pack for 5 gallon should be good... so 2 packs should work good.
And finally, you would get approx 6 gallons of wine after racking so about 28-30 750 ml bottles.
Good luck. Let us know how things go.