When it enters the field, it creates treasure tokens based on the number of artifacts and enchantments controlled by opponents
If you do cast it from your hand, rebound will work regardless of whether you paid its mana cost (for example, if you cast it from your hand due to Maelstrom Archangel)
You gotta put the -1/-1 counters on something
A 0/5 is pretty hefty to burn or kill in combat and always feels like a waste to use dedicated removal spells on it, particularly if they have already had use from it
You can keep pumping out resources turn after turn, but be aware that if you start getting low on life, there's not much you can do to stop it with Black Market Connections since it is guaranteed to trigger at the top of each turn
I personally see a distinction between hard casting from the graveyard and reanimating a creature