One of the things mentioned in the charges is the fact that his home computer shows he connected to Tor multiple times. Can anyone point to any online resources that address this as legal precedent or not?
The duty of the prosecution is to prove their case in court. The fact that they have seized his computer(s) and carried out forensics already, means they are looking hard for a conviction. If they freak him out with this sort of circumstantial evidence, he will say something, and it's never a good thing.
https://www.youtube.com/watch?v=d-7o9xYp7eE
Legal precedent depends on jurisdiction and you haven't shared that. Connecting to Tor is a 'fact'. What value that fact has is up to the prosecution to prove. Relevancy is key. Best to wait and see what they alleged happened and then challenge just those set of facts.
If he says nothing, they have a lot to prove. In many places in the US, they will come in with multiple felonies then accept all sorts of plea bargains as it drags on and on and on, like a bad used sales car man.
He would of course be permitted to make an argument as to why that circumstantial evidence is weak and should not be given any weight.