A: Washington is an at-will employment state, which means that those employees whose jobs aren't protected by an employment contract, collective bargaining agreement, or some other similar protection (i.e., most of us) can be terminated without cause (i.e., without grounds) as long as the termination wasn't based on the employee's position in a protected class (i.e., gender, race, etc.). In short, unless the reason for your friend's termination was because of race, gender, age, disability, etc., the termination likely wasn't wrongful.
A: Well, if you believe you were retaliated against by your employer because you had an open L&I claim you can file a retaliation claim with L&I within 90 days of your termination. You could also consult with a private attorney to see if there are also grounds for a lawsuit for wrongful termination (you haven't provided enough facts to make that determine based on your description). Good luck.
A: Sometimes. The CBA will often describe what the remedies are the process that should be followed if the CBA is violated. For example, a lot of CBA's require arbitration. I suggest you get a copy of the CBA and see if the Union will represent you or go see a private employment law attorney. Good luck.