How Does The "Franz" L-Deck Occupation Work?
The last sentence on the German card is a bit clearer:

Wenn du Franz ausgespielt hast und bei Spielende nicht mehr hast, kannst du "Ich bin nicht Franz!" sagen und erhaelst 1 Sonderpunkt.

That is: "If you played Franz and don't have it any more at the game's end...".

Which says that you only receive the bonus point at the end of the game. The condition here is slightly different from the one on the English card. If you play the card, pass it, get it back, and play it again, you do not receive the bonus point. The German card is not clear about what happens if you play it, pass it, get it back, and keep it in your hand.

As for your other questions: I think you're right. The card has to be played first before it has any effect, just like any other occupation. In combination with the Simplifier, Franz has no effect: it cannot be passed to another player, and gives no bonus point.