I am making a 2d eagle-eyed view shooting game that uses space to shoot. (The bullet is a long straight line)

I have a few simple questions I hope someone could answer for me:

1. How do I add a 'reload' effect so that someone playing the game can't just hold down space for a rapid fire?

2. How do I make the bullet stop at one person in a situation like this:
----- --- but not having it go through the 1st guy.