When purchasing from "Ali" as you did, keep in mind that "silver", "gold" etc. should be assumed to be adjectives, not nouns. They refer to the color of the product, not what it is made of. So one should assume that "Silver wire" is just wire that is silver in appearance.
I fully trust you that it is thicker than advertised, since the production cost is probably higher for thinner wire that must be very carefully drawn out more times to make it super thin. The material cost is practically nothing in either case. This is the exact opposite of thick wire, where you would be more likely to get something thinner than promised due to high material cost.
The second and third issues:
-does not make electrical contact with DMM probes
-hard to solder, takes a few seconds, after which it makes electrical contact at the solder joints
...is entirely consistent with wire that is insulated with some type of varnish. This is normal and expected for board "bodge" wire so that it doesn't short out anything between connections, and you can cross several wires without issue. The varnish is designed to be soldered-through (not mechanically removed), and is very thin and practically invisible. With correct iron temperature and a decent flux, it is usually easy enough. If the varnish isn't exposed to fresh hot flux as it is heated, you might have a hard time. This varnish would not likely explain the high diameter, as it is very thin.