I'm not a Washington lawyer, but after doing a little research, my guess would be that your late husband's father probably isn't going anywhere.  As the surviving spouse, you're entitled to all of the community property, and it looks like your state assumes that everything is community property unless proven otherwise;  separate property would be anything that your husband had before the marriage or that he got as a gift.  Your husband's father would be entitled to 1/4 of the separate property (you get the rest), but he'd have to prove that there was separate property.

That would probably be difficult, aside from anything he might have given your husband as a gift himself.  And it's possible that it's simply too late, at this point.  You should talk to a local attorney, for reliable advice based on a bit more factual detail.

I am a Washington attorney and I agree with the response from the New Jersey attorney.  You are entitled to all the community property after your husband's death.  If your husband's property that you have left was ONLY community property, then it's all yours.  If any was property he acquired prior to marriage or as a gift, those would be separate and his father would only be entitled to one-fourth of that separate property.  All that assumes that his father will start an action in Washington to recover the property.  If so, then you should get yourself an attorney.  Fines given in probate matters can be very stiiff, so be careful how you handle this matter.