[MX] A few AS questions, should'nt be too hard

I’m making a game that will eventually be like asteroids kinda. I have this line for a turret that rotates around with the mouse. For the turret that rotates im using the code:

[AS]onClipEvent (enterFrame) {
myRadians = Math.atan2(_root._ymouse-this._y, _root._xmouse-this._x);
myDegrees = Math.round((myRadians*180/Math.PI));
_root.rad = myRadians;
_root.deg = myDegrees;
_root.rad = myRadians;
_root.deg = myDegrees;
this._rotation = myDegrees+90;

The first question is how do you make it so that the turret thing rotates on an endpoint and not rotate by its center?

The second question is when I press spacebar the turret shoots a little MC but how do I make it fire in the direction of whatever the angle is. Like if myDegrees = 74 degrees how do I make it fire at a 74 degree angle?