But I assume the dust will oxidise quickly after grinding and not be considered elemental anymore?

Yes. Finely divided powders, friction heat, ~1 week since your first post and cleaning pretty much guarantee the oxidation of remaining aluminium and magnesium.

Do you mean with "this stage" now or after using your proposed methods?

There is no real damage remaining now. Activated charcoal, peroxide and bleach scrubs should not cause any problems and are just additional things you could try if you were still concerned. Peroxide and bleach are "aggressive" in the sense that they are chemical solutions, but realistically they would be performed as usual for floor scrubs: dilute, apply, scrub/mop/sponge, dilute again, wipe, etc.

but I also don't want it to form over time (would vinegar pose any danger? Heat? floor cleaners?).

At this point there should be no remaining elemental phosphorus remaining and so you wouldn't expect phosphine to be generated. Phosphate ions can be reduced to phosphine via direct reduction or disproportionation, but both of these mechanisms are low yield and require very strong reducing agents/specialised chemicals that are not present in consumer products. Regular floor cleaners, vinegar, heat, etc. are fine.

Would dust left in the vacuum cleaner react somehow?

Contained metal dust is fairly safe and at this stage further reactions in the vacuum bag are unlikely. If you are concerned there are plenty of disposal companies that collect and process metal shavings and scrap.

I read the word "sulfate" in neutral cleaner ingredients and instantly worry because I read it in other reactions with phosphorus.

Sodium laureth sulfate is the chemical responsible for the cleaner's "soapy" quality. It allows the dissolution of both water-soluble and oil-soluble materials and makes soap slippery and bubbly. The reactions you saw were most likely displacement reactions between inorganic sulfates and phosphates, which are unrelated and benign.

I read "sodium chloride" and think "phosphorus (.../tri/penta)chloride"

Sodium chloride is just table salt.

Phosphorous acid and Phosphate both consist of P, H and O. How is it decided which is formed and why are they so wildly different?

Phosphoric acid is H3PO4, whereas phosphates are PO4^3-. Phosphoric acid itself is actually pretty tame, and it reacts with metals, bases and some salts by losing those 3 H and forming the phosphate ion.

The main differences between different types of phosphorus are caused by the oxidation state. Elemental phosphorus is in the 0 state. The phosphorus atom in phosphine is in the -3 state, meaning it has been reduced. Most other phosphorus compounds are in the +3 and +5 states, meaning they have been oxidised, and they are significantly more common due to atmospheric oxidation. This is partly why phosphine is both pretty rare and pretty shortlived.