If a pskyer is going to cast Protean Form, and chooses to use a sacrifice to perform it, how should the ongoing effects of Protean Form be handled? Is it the psyker who is affected by the psychic phenomena, or the sacrifical subject?

This then leads into another question, can multiple sacrifices be used?

That's an interesting question that luckily won't come up - Corrupt powers can't be fueled with Sacrifices.