On the soldering, you’re not really getting the back of the pot hot enough to properly melt the solder. As a result it’s all ‘blobby’ and sitting rough and proud of the surface. It should have a rounded smooth, shiny surface to it.

I don't know what size iron you have. An 18W-20W iron is fine for small electronic components, but you really need a 50W-60W iron for soldering to the rear of pots, and ideally temperature controlled and with a fairly large tip that has some heat storage capacity so it doesn't immediately cool down when you touch the back of the pot.

From the resistance measurements, it seems there's enough contact for the moment, but you are fairly close to having a few dry joints, and these rough solder blobs can allow oxidation to creep under them over time.

It helps if you apply solder ('tin') to the back of the pot and the wires first, before putting them together and heating them up. Solder will stick to solder more easily than solder to the metal, so it just makes life that bit easier.