Re: Silver Solder question
Agreed. The higher the silver content, the harder the solder and the higher the heat needed for proper bonding.
I personally prefer flux, but the rosin core is fine for electrical work and much easier to use.
The better you clean the joint, the better it will work regardless of which you use.
At the higher percentages, you're likely to damage the cable itself since the required heat is so high. I like 60/40 for most heavy duty soldering.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.