Does Moomoo Cheese allow you to heal 30 damage each from up to 2 of your Pokemon, or does it heal a total of 30 damage between the two (like 20 on one and 10 on another)?
Each Pokemon you choose for Moomoo Cheese gets to heal 30 damage.
Source:
Vivid Voltage FAQ (2020-10-31), TPCi Rules Team (2020-11-12)
For Billowing Smoke, since prize cards are discarded when the Pokemon it's attached to gets KO'd, how does this interact with Dubwool V's "Revenge Blast" attack that "does 30 more damage for each Prize card your opponent has taken"?
Revenge Blast does not count any prizes that were discarded due to Billowing Smoke.
If I play the Will supporter that lets me choose heads or tails for my first coin flip of an attack, do I get to use Will's effect again if I use Glimwood Tangle stadium to reflip the coins?
Yes, if you use Glimwood Tangle, Will lets you choose heads/tails for the first coin of the reflip.
Can I use both Victini's "Victory Star" Ability and Glimwood Tangle stadium to reflip coins from an attack twice?
No, you cannot. You can use either the ability or the stadium, but not both of them. As a general rule, you can't use more than one reflip effect at a time.
If my already-poisoned Pokemon is hit by Dragalge's "Poison Cultivation" attack then I use Switch while Dust Island is in play, is my new Active Pokemon poisoned with a regular condition (only one damage counter in between turns) or with the effect from "Poison Cultivation" (ten damage counters in between turns)?
If the Poison effect places more than one damage counter during the Pokémon Checkup phase between turns, then switching the Pokémon out using a Trainer card while Dust Island is in play will retain the modified Poison effect of placing multiple damage counters on the new Active Pokémon.
How does Billowing Smoke work with Greedy Dice or Jirachi {*} and its "Wish Upon a Star" Ability?
If you KO a Pokemon with Billowing Smoke attached, you do not get to use Greedy Dice nor Wish Upon a Star since neither of those cards would be going into your hand. Any Prize cards that would be taken for a Pokemon that has Billowing Smoke attached are discarded, not taken.
Source:
Darkness Ablaze FAQ (2020-07-31), TPCi Rules Team (2020-08-13)