Your circumstances are very complex. It is not possible to adequately address the numerous issues raised by your question in this forum. Each of you need to meet with an independent attorney who can advise you how you should proceed to protect your own interests, and to the extent that you intend to do so, the interests of the other party. I recommend that you each should consult with legal counsel right away.
The suggestion that you consult with independent counsel is really for your benefit. You need not worry that two attorneys will be likely to create a conflict between yourselves. Each of you will have the right to make whatever decisions that may be deemed appropriate without regard to the recommendations by your attorney. It is just very dangerous for one attorney to attempt to represent the differing interests that each of you has in this situation. If it is subsequently decided that the attorney had a conflict of interest, that may erode the protection that you were seeking in the first place.
Since you are not married, the community property laws of the State of Washington do not apply to you. However, as you are no doubt aware, we now have important legislation that may provides some definition and protection for couples who intend to enter into a domestic partnership relationship. That is why it is so important for you to consult with your own legal counsel. You need to be certain that the attorney that you select is familiar with the domestic partnership legislation, and is comfortable providing legal counsel in this field.
But whether the domestic partnership law applies in your circumstance or not, you each need to take steps to protect yourself and your partner. In general, I would expect that your attorneys are going to recommend that you enter into a formal written Domestic Partnership Agreement by which you will specify your intentions with respect to the ownership of the assets that you own separately and jointly. Each of you will also probably need to sign a Will to provide for the disposition of your assets in the event of the death of one or both of you. Finally, you will each probably need to sign a Durable General Power of Attorney to authorize someone to act as your agent in the event of the disability of one or both of you.
The most dangerous condition is your present situation. You may feel that you have a clear understanding between yourselves with respect to your assets, and the arrangements that will be followed in the event that you terminate your relationship. However, in such a circumstance, it is almost inevitable that each of you will see things differently, and be inclined to seek any advantage that may be available. Also, if either of you were to die, your understandings would be of very little value in the context of claims that might be made by other members of your family. It is critical that you attend to the documentation of your intentions.