1. LX will check your bag through, but will collect the fee for GVA-MUC.
2. There is no such thing as "linking". All carriers do is put a note in the two records, but it is to make you feel good and does nothing.
3. Remember that if you no show for your MUC-ORD departure, your ticket will be cancelled and will retain whatever value it retains under its fare rules. You may well be required to purchase a new ticket at walk-up prices.

For this reason, I generally suggest allowing 2-3 what the MCT would be for a connection.