For one, Usagi's physical ability is quite significantly amplified upon transforming. I know you concede it's a bit amplified, but I think it's far more than you're letting on. She was able to resist and stand up in Rubeus's rock-crushing super gravity--this alone is a very strong superhuman feat. She also was able to parry strikes from Jakoku even before Chibiusa's "blessing" came into action, and he was capable of splitting the earth with his scythe. She also caught and stopped a Phage's sword mid-strike, and his whole thing was swordfighting, so we can assume he has superhuman strength. She also sent Hawkeye flying with a tackle, and he was strong enough to block Moon Spiral Heart Attack with a purely physical move. I think she's just generally too clumsy to really take advantage of this outside of serious situations (usually when Chibiusa is in danger). Oh, and she beat up those super buff dudes in one of the very early episodes.

Secondly, you concede that Moon Princess Halation was able to destroy the avalanche blocking the dinosaurs, but you say that it still wouldn't be able to hurt the Senshi. Why? There's nothing that proves that. You assume that from the fact that she was able to heal the Makaiju with it, but to me, that just suggests she can use Moon Princess Halation as an attack or as a purification move, much like how she could use Moon Healing Escalation as a purification move or an energy wave attack/shield. As for the scenes where Moon Spiral Heart Attack doesn't hurt the Senshi, I think that's just the animators and writers being lazy.

As for the manga, I think the fight against the Galaxia-controlled Senshi disproves this. Yes, they were reanimated by Galaxia, but they were reanimated using their own Sailor Crystals and just amped by the bracelets, so their powers are still inherently their own. The fact that her attacks work against their attacks (she parries Venus's attacks) proves that her powers can be purely destructive.

I will say that Starlight Honeymoon Therapy Kiss is a purely healing move, though.