“Mediums? Channeling? Demons?”

My mother passed away a while ago, and her husband wants to put her on a Mormon list to be married eternally. Is that okay? What should we think about channeling and mediums? What about Halloween? And demon possession? Is the church replacing Israel? Is there a second blessing or second portion of the Spirit we receive later? Why did Absolom say he had no successors if he did indeed have children? Is mental illness different from demon possession?