A. Soulless makes the base reward 0 Power, rather than 1. The Yithian’sPossession adds to whatever the base reward is, whether 1 or 0. Thus, aYithian who Captured a Soulless Tcho-Tcho still provides at least 1Power.
A: No, they (like Yog) are Controlled Gates without having a Controlling Unit. However, The Invasion controlling the Shadow Pharaoh seems hilariously over-powered. Remember that with The Invasion it is virtually impossible for them to be First Player early in the game, so someone else should acquire Shadow Pharaoh before The Invasion can.