ANSWER:
1. Including the Prophet (salla Allahu alaihi wa sallam) in your Qurbani is an innovation as he is already credited whenever his Ummah follows the Sunnah.
2. No problem in this, however, only one sacrifice is sufficient for the whole family living under one roof and eating from the same kitchen.
3. This is permissible but the Sunnah is to include the dead in your own sacrifice.