Only ground ONE end of the shielding (typically the ECU end). If you ground both ends, you've just made an aerial...
Dunno about that Paul. Other way around I reckonhttps://en.m.wikipedia.org/wiki/Talk:Shielded_cable#Grounding_Cable_ShieldsAnd there is another bit slightly further up about grounding both ends
If you have the correct crimpers and have prepared and crimped the terminals correctlyYou do not need the solder it jus causes a stiff area in the wiring where it will fatigue and crack All the connections in the tin birds are crimped this way .