The reason that this is the actor playing Pippin's first time in the role is everyone else who's ever played it commited suicide at the end.
Either they burn up, or they forsake the role (which specifies a young man desperate to be extraordinary) for an ordinary life outside the show. Either way, they never play the role again.
I could be wrong on this, but Catherine is a widow. Each of her "husbands" was a Pippin that was incinerated in a previous show. She finally stands up to the leading player because she is tired of losing those she loves.
"No Time At All," Berthe's song about living as much as you can during the time you have on Earth, isn't meant to show Pippin the meaning of life. It's a warning about the finale.
Or it's encouragement to burn himself out, since "Berthe" is just a character performed by one of the players.
"When you're as old as I, my dear, and I hope you never are..."
The Leading Player responds to Pippin's near-breakdown at the end of "On the Right Track" by laughing and telling him he's, "on the right track". Pippin's breaking down is the right track to wanting to commit suicide.
The Finale completely changes the line from the opening number, "We've got magic to do, just for you," once the audience has been encouraged to take Pippin's place, and been told that the players are already in their heads. Since so much is made of the "magic" being taken away when Pippin chooses ordinary life over self-destruction, it implies that right from the beginning, the audience has been ensnared in the same kind of madness as Pippin, and just by viewing the "show" the viewers prove their potential to become part of it.