User blog comment:EmpyreanSmoke/Supernatural Q&A/@comment-207.244.77.1-20150929202547/@comment-24834479-20150929234946

1. He was able to channel so much power that he created a seal over the darkness's prison.

2. He would have been immortal, and had his other powers enhanced.

3. I don't think that it could fully corrupt him, as he was strong enough to withstand it.

4. No.