Okay, I want you all to be honest with me...
Is this really because you all want explicit proof or evidence that Super Mario characters can destroy a galaxy? Is that the norm for anyone in fiction performing creation feats?
I mean, looking at this from a logical perspective: if I had Galaxy level Attack Potency via something like creation, that should mean I can deal Galaxy level damage via means like creating something like energy beams or whatnot with the same potency, right? And if said characters can withstand it, then they by definition should have Galaxy level durability, no? You do realize that just because someone has a certain level of damage they can inflict on others like Country level via a calculation doesn't mean that they can actually destroy a country, right? Donkey Kong may have Island level AP due to his moon punching feat, but that doesn't mean he can destroy an island with a single punch. And it's not like he actually destroyed the moon, anyway; he only knocked it out of orbit.
If you guys are really that doubtful on giving Super Mario characters Galaxy level striking power and durability, why don't you simply give them "possibly Galaxy level" attack potency and leave the other two statistics as they are?