Apparently I read somewhere that Eitri might have put a spell on Stormbreaker in IW. That's why it shrugged off the beam of all 6 Infinity stones like nothing. Of course, Thanos was unprepared in IW as you said. If he had used the actual powers of the stones then it might turn out differently.
Scarlet could also change the density of an object. Remember when she pushed Vision through the building in Civil War? Also she ripped Ultron's core out of his body to kill him. In theory she could also do that with human internals (would be much more gruesome tho
).
I'm not most well versed about Captain Marvel's powers in the comics, but in the MCU I don't think she needs to absorb any kind of energy before projecting those proton blasts or turning binary (her super mode that goes through spaceships like tissue paper). It's just something she innately can do (once that controller chip was removed in her solo movie). In the final matchup, we see that she's on par with Thanos strength wise and only the power stone could knock her back. I'm intrigued actually what would happen if Thanos used the space stone against her, since that's the original source of her powers.
Stormbreaker doesn't have Odin's "worthiness" spell, so yes anyone can lift it if they're strong enough. By extension though, it also can't produce lightning on its own (that has to come from the wielder). Compared to Mjolnir which has the worthiness spell, but if you are worthy, then you gain full access to Thor's powers (that's why Cap could also summon the lightning when he used it). "Whoever he shall be worthy, he shall possess the power of Thor" is the full enchantment.
The stones missing creates an interesting paradigm. It could be that they have served their purpose in Thanos' final snap to destroy them, so that's it and the universe will be ok. If you've watched Spiderman's new trailer there's some talk about multiverses opening up... And of course don't forget there's Loki on the loose with a space stone somewhere...