Excel has a function built in for Standard Deviation, but I don't know what it's supposed to demonstrate in this context.
OP, we can't check your formulae because they don't show up in a .PDF.
It would also help immensely if you just reformat to landscape orientation so all the columns show up on one page. Also, do you have sufficient data to break down "Firearms" into handguns, rifles, and shotguns? Showing how few murders are actually committed with rifles could go a long way (except for the Feinsteins of the world) toward showing just how foolish banning AR-type rifles is.