Hoisin, this problem is not caused by your guitars or your cables. Your ground connections works properly, because the hum disappears when you touch the strings/metal parts. 
Lifting the components off the shielding is wasting your time. In a passive guitar circuit, ground loops are non-existing, so you gain nothing. Your digital devices is the source to your problem. 
Some parts in a signal path  - effect pedals, preamps, amps...you name it - do simply not work well together. But as long as the hum disappears when you touch the strings, you should be ok  99,99% of the time Wink