To determine a spell's total cost, start with the mana cost (or an alternative cost if another card's effect allows you to pay one instead), add any cost increases (such as kicker), then apply any cost reductions
Cards like Viscera Seer become your best friend, as well as stax cards
The choice between an English or Japanese booster box really depends on what you are looking for
While Abzan toughness decks can absolutely assemble massive walls and defenders, the archetype struggles to keep pace with faster value engines in todays Commander meta
I wouldnt say its a bad play, but it is still above the baseline of what you really want to be paying for that extra card (2 mana)
Carrion Cruiser I imagine Carrion Cruiser mostly sees play in Peasant Cubes, but a Gravedigger that supplies its own fodder could probably find a home in slightly stronger Cubes as well