Not so. Lincoln sent the fleet a week before Davis fired.
Had Lincoln landed supplies at Sumter then what? How would that have constituted a threat to the confederacy?
Then the fort would have had greater ability to be used against Charleston. Your reasoning in this is quite amusing, BTW. Translate it into modern leftist context and you should see why: "Had Saddam Hussein simply bought a bunch of uranium then what? How would that have constituted a threat to the United States?"
Was Charleston blocked? No.
It could have been on a single command. The guns of Sumter controlled access to Charleston harbor.
Were the people in danger of being bombarded? No.
They could have been. A single command from Lincoln could have ordered Sumter's guns to fire on any civilian attempting to enter or exit.