How does it work with creature abilities? For example Puffer Fish. Does it poison you when it heals because it's effectively attacking yourself with an anti-mattered creature, does it poison your opponent, or neither?
-in regards to poison, my hunch would be it is turned off as it is not damaging, much like vampire.
Does an opponent's (or your own) Gravity Shield prevent the "attack" from functioning the way it prevents opposing anti-mattered creatures from attacking? What about other shields?
-they do not reduce the healing you receive, but when antimattered they do reduce the damage done, as noted in the... notes.
Does sundial prevent this card from healing you for a turn?
-yes, just as antimattered creatures do not while sundial is out