This is a difficult question to answer without knowing all of the details of what was happening during that period of intense settlement offers back and forth. Your attorney does have an ethical obligation to convey all settlement offers to you, and to allow you to make the decision as to whether to accept or to proceed to trial. Moreover, the attorney cannot put her / his own financial concerns ahead of your stated goals in the representation. That being said, it doesn't really make sense to believe that such was the case here. Few attorneys believe that withdrawing is the way to get more money out of a case. Nor does the attorney have a contract with your ex, or any obligation to pursue fees from the other party after the representation has ceased. You can always file a complaint with the Bar association. The address is: http://www.wsba.org. They will inquire of the attorney, who has a duty to respond.
Without knowing all of the details, reviewing documents, and interviewing witnesses, no person should assume that this Answer constitutes specific legal advice for any specific legal situation. No attorney-client relationship is created by posting general legal responses on this site.
If I understand your situation, you were in a divorce when your attorney withdrew. Is that correct?
If you file a grievance against your attorney, the Bar Association will only investigate if they feel the attorney violated an ethical rule. Your question appears to be based on an assumption that it is unethical for a lawyer to withdraw prior to the case going to trial. That or you feel that he did not like your decision to not sign a document during mediation or a settlement conference. It is not unethical to withdraw from a civil case because the client cannot pay the lawyer's fees. Your written fee agreement should spell out conditions for the attorney to withdraw. If it does not, I do not think this is an ethical violation, and technically, although the Bar Association says fee agreements "should" be in writing, if a lawyer is dumb enough to not have it in writing, this by itself is not an ethical violation.
First off, we can't read someone else's mind. Your lawyer did not tell you that he was threatening to withdraw if you did not sign that document or take the offer. If you owed him money and the trial was approaching, the lawyer has the option and right to withdraw from the case. Not being paid is a legitimate basis for withdrawal from a civil case. On criminal cases, withdrawal requires permission from the court. If the lawyer filed a Notice of Intent to Withdraw, and he provided you with at least copies of the file materials if you requested them, then he probably complied with the rule on withdrawal.
A lawyer must take reasonable steps to protect the client's interests prior to withdrawal, but if the client cannot afford to pay the attorney, no one is going to force the attorney to continue working for free on a civil case unless for some reason the opposing side objected to the withdrawal and the court held a hearing and they refused to approve the withdrawal.