Oh yea! You’re right about the ground lug ring…I forgot about that! I was thinking you were talking about one of the pins on the depth pot. But you can certainly use that as a ground reference.
That solder is probably ok, but I’m always a little skeptical of generic Chinese made solder…I’m sure some Chinese solder is great, but I know others are not. I depends what kind of flux they are using and what kind of tin/lead alloy they are actually using…and how many contaminates it has. Those things make a difference in how well the solder will hold and flow, and also in how easily the solder will keep from being oxidized. This is the stuff we use:
It’s more expensive, but we know what we are getting. Partial rolls are available on Amazon too (it comes in little tubes).
-Brach