1. No. Your wife may not use your UG. When you do not board at T-15, your ticket will be cancelled and your UG will go to the next person on the list. She can't scan your BP and take your seat as the pax count will be off. The aircraft won't move until they figure it out. At that point, you will be off-loaded and she will be punted back to Y (if she is lucky and not punted off the flight for having delayed its departure).

2. If you no show for any segment, all remaining segments will be cancelled. Whether your ticket retains any value will depend on the fare rules for your ticket. If a standard non-refundable ticket, you may have some credit less a $200 penalty.