Grounding for sub panel breaker
The ground retrofit rules say you need to take the ground back to the same panel the circuit comes out of.  So maybe this ground you just installed actually goes to the subpanel, and the subpanel has its own ground wire back to the main.  

Also, I would flip that around, and make it so the fuse box is a subpanel of the breaker panel, and have it be powered off an AFCI breaker.  That will be a good hedge against most aluminum-wire troubles.