QIf my leader has 1 defense and I play this follower's Fanfare ability, do I lose the game?

AYes. Because confirmation timing happens after the Fanfare ability has resolved, you will lose the game before the automatic ability can restore your leader's defense.

QI have 2 copies of this follower on my field. During my turn, if my leader loses defense, will each of their automatic abilities trigger?

AYes, they will. Note that each copy's ability has a separate limit of 4.