The chopsticks thing - as explained in a video I saw on a documentary TV program about funerals in Japan, the sticks left in a bowl resembles the post-cremation long bones in a large urn, that are passed around the family in some kind of ceremony, and the sticks in the bowl either remind, or are symbolic, of death..
This is the explanation of why you don't pass food around with chopsticks. At the funeral, after the cremation, you line up and then with another person, pick up a piece of bone with chopsticks and stick it in the urn. The first time, I was so afraid I was going to drop it! And then what would I have done? Pick it up with my fingers?