Now you said, "The main gallery of guns at Sumter was pointing towards Moultrie to complete this broadside attack from north and south", And I would agree with your logic. And if the other confederate positions were not effective to fire on Sumter, and Moultrie was their main threat, why was Anderson men mounting extra guns? As I pointed out the moving and positioning those heavy guns to be loaded and fired requested a larger crew. It didn't make much sence to shift those men from gun to gun because once in position the firing of the gun was the easiest and quickest part of the whole operation and you had to repeat the process all over again.
The only thing that the men in Fort Sumter could have done to aid the ships running the blockade to reach their wharf and unload supplies and re-enforcements was to have fired the forts guns against the most dangerous batteries to the Ships. I agree that Moultrie would probably have been that danger. But why mount extra guns if you can not fully man the guns you already have mounted? And surely the mounting the extra guns would have been taken as it rightly should have been, as an act of aggression.
The popular opinion that I have seen as to why Anderson was mounting these 5 extra guns was as a "make work" project. AND that makes some sence. But if that became obvious to his men that they were just being kept busy and that there was little purpose to their work, then Anderson would have had a moral problem. There was also a food problem and the amount of rations that these men were recieving while doing this work.
Again many pundents remark that Andersons men were not motivated, because they only mounted 5 extra guns during the 100 days that they were there. Again I contend that 5 guns were all that were necessary for them to mount, and all that they could have manned with their numbers. They were not there to finish the work on the entire fortification. Those 5 guns that were mounted had to have been done for a purpose.