I can't quite correlate what you wrote with the pictures. But from what I can see in the pics, it looks correct.
In a nutshell - there should be no other connections between the battery negative terminals and the shunt. Everything on the negative buss goes through the shunt even the battery charger.
Another observation is that small red wire from the shunt that is connected to the battery negative terminal on the shunt. I think that is actually the +12V that powers the smart shunt and needs to be a fused wire to the boat's battery positive on the battery. Check the installation instructions to make sure...
One other comment is that is quite the "rats nest" on the batteries; Should you have an issue and need to get the batteries disconnected it would be quite the challenge. I would consider installing a positive buss bar and move all of those connections to the buss bar and have a single cable to the batteries. Something like this - https://www.bluesea.com/products/1993/PowerBar_1000_-_12_5_16in_Terminal_Studs
Hope this helps
In a nutshell - there should be no other connections between the battery negative terminals and the shunt. Everything on the negative buss goes through the shunt even the battery charger.
Another observation is that small red wire from the shunt that is connected to the battery negative terminal on the shunt. I think that is actually the +12V that powers the smart shunt and needs to be a fused wire to the boat's battery positive on the battery. Check the installation instructions to make sure...
One other comment is that is quite the "rats nest" on the batteries; Should you have an issue and need to get the batteries disconnected it would be quite the challenge. I would consider installing a positive buss bar and move all of those connections to the buss bar and have a single cable to the batteries. Something like this - https://www.bluesea.com/products/1993/PowerBar_1000_-_12_5_16in_Terminal_Studs
Hope this helps