[Zeke]

Infinite means just that, open. If both ends are disconnected you should see Ohms when you attach at each end. If you identify each wire and why it is there, that's a start. If you label these and verify each device as working, you're almost there. It's the combination of all those wires in one JB that bothers me.

Or you could determine which wire is the line feeding this bundle and remove one wire at a time to see which one is causing the breaker to open. Worst case is you have to have all devices working the throw the breaker which is a simple overload.

One by one will tell you that there might be a short in just one load circuit. Check the wiring at each device for reverse connections or something touching ground when the connection is closed up.

Is everything grounded either by bare, green or conduit itself? (To code or not, you want to understand how the grounds exist if they do.)