Prompt return fire
Return of fire from who? the SS in the follow up car ( which was practically inline with the 6th floor window when the 1st shot was fired) or the cop across the street?
Not at all if Oswald done this he would not be concerned, about getting shot at, in fact he would have expected it, and would have taken his revolver to work as well, just in case he got into a close range firefight, with someone like officer Baker while on the way out of the building.
The reason for the shots being fired onto Elm was because it was not possible to hit close to the limo from the Dal Tex fixed firing point, until it made the turn.