1. What is good for the soul?
Self-realization. Love, though not the kind you get in a Hollywood movie. The kind that brings peace and understanding (what I would argue the term really references anyway).
2. Is it important to be good to the soul?
Yes, though I'd add that I think being "bad" to the soul takes some pretty conscious acts of suffering in this life. There is always something to learn from any moment, no matter how heinous the event granting the lesson. Suffering isn't remotely necessary or "good" for the soul, but it does bring forth growth.
Anyway, being good to the soul is being good to all seen before you. Absolutely important.
3. Is there a difference between what is good for your own soul and that of others?
Not in a meta sense. Self-realization is a universal "good," I'd argue.
Now, if one wants to nitpick about likes/dislikes or personal inclinations, then sure there are things "better" for one than another. I'm not fond of heights, yet some people never feel more alive than when skydiving.
4. What is the most soulful experience you had this month?
Reconciling with an old friend. Properly reconciling. Being open and self-admitting errors made in actions/words. Actual mending of the soul for both parties.
Really, just anything that involves improving one's self through a positive moment with another.