Similar lists do exist in Legacy, but those fall more on the side of Death and Taxes, which is a lot better for interacting with the opponents gameplan
Five mana is steep, and is going to be difficult to find a spot for, but winning via combat damage in a deck that can throw down a half-dozen creatures every turn is a very real outlet that needs to be considered
Enchantments There is a pretty sizeable pool of one black mana, when this creature dies, it doesnt die/returns to the field, both on enchantments and on instants, so Im not going to talk about those right now
Probably not, but it may be enough to make for a fun jank brew
Since the duos activated ability scales its damage based on your Dogs in play, a Dog-centric brew is your best bet here