I would run the ground wire for the coax and other things back to the panel. Much better than relying on the conduit.
As for the additional ground rod, I am not sure... In general more grounding is better but they do need to be connected together well and I am not sure of the code issues. The most important thing is for all the grounds to be connected. I have seen a small ground rod added for telephone or TV - this is a very bad practice and not allowed by code. The two ground systems can have substantial voltage between them.
As for the additional ground rod, I am not sure... In general more grounding is better but they do need to be connected together well and I am not sure of the code issues. The most important thing is for all the grounds to be connected. I have seen a small ground rod added for telephone or TV - this is a very bad practice and not allowed by code. The two ground systems can have substantial voltage between them.