That's the $64,000 question...
I'd suggest reading the relevant RCW's, reading some related case files and court opinions, then you should have a pretty good idea. While there are a few "black and white" answers, there are very few "black and white" situations. The world is filled with gray and everything you do will be dissected and analyzed in the bright light of day. A split-second decision you made will be gone over for hours and hours.
Anytime you resort to deadly force, you put yourself in legal jeopardy. Even if you do everything "right" as you may still be charged and/or sued. Even if you win, you will have spent a lot of money to defend yourself.
It is not to be taken lightly.