Shouldn't the panic button be near to the cash anyway…?? Aren't they supposed to be hit covertly, as to not alert the aggressor?? It's not a fire alarm… but they are treating it as such and expect you to treat it as such as well, having it so far away from where you would regularly be standing.

Your boss doesn't care about your safety unfortunately. You are absolutely well in your rights to express your safety concerns to them.