I have no idea of what the law is in Washington, so my first course of action would be to take all the paperwork on your land to a real estate lawyer and have them decipher what the easement says. Until you know that, there is no point in doing anything else.
Here in Texas, I've worked for clients that had easements to get to their homes, and clients that had easements across their place to get to homes behind them. In every case, it's a problem. Some have gone hostile and sabotaged the road to make it as bad as possible to get through. In one case, they cause the people renting the house to move out and the landlord lowering the rent to the point that some crackheads moved in. At another place, they culverts where removed. Mother Nature was blamed for this, but I don't believe she had anything to do with it. And at another place, the road was so word down by lack up maintenance that the water lines from the street where exposed and damaged. The guy at the end of the road tried to blame everyone else on the road for destroying his water lines, but when he tried to sue to have the other home owners pay for it, nothing happened because they said that the lawyer was bluffing and there was nothing in the easement that covered that. And his refusal to pay his share of costs to maintain the road invalidated the easement.
Back in CA, a friend had some land that was land locked by a State Park. He had two easements through the Park to get to his land. His easement was rock solid, but they wanted him to sell them his land, so they started harassing him and everyone that used the easement. They would send Park Rangers to sit at the gate and block it, and then refuse to allow anybody through it. We took pictures of them and he sued the park for a significant sum, and won. Then they changed the road through the park and said that the easement didn't allow anybody to use the new road, so he sued and won, forcing them to fix his road and make it accessible for a fire truck to get to his cabin. Then they closed down the road because it interfered with some type of endangered salamander. He sued them again and won because that endangered salamander never existed anywhere near his land and they had lied about it being there. The thing about this guy is that he enjoyed fighting the Park and going to court. Overall, he made money on them. He even built a pond on his land and when they took him to court over building a pond without a permit or environmental study, he claimed that the pond had been there for a hundred years and he was just cleaning it out and repairing the damage to the dam. He won that one too!!!
I have no idea what the solution is for your easement issues, but just wanted to share with you some things that I've encountered. Hopefully you can resolve this quickly and cheaply. If not, look for loopholes in the easement that you can use to cancel it, or force them to pay for damages that will make it financially impossible to continue renting the place out. And if they don't pay, allow you to file a lean on the land with ridiculous interest rates.
Good luck.