Does giving a landlord a "tentative move-out date" constitute a mutually agreed upon date?

The best time to consult with an attorney is BEFORE you act. In Oregon, as to when the tenant can be forced to vacate on month-to-month tenancies, normally landlord's are required to give at least 30 days notice (more if you have lived there for more than a year). And, the notice must be given in the particular way defined by statute. There are several things that could have been done before you vacated voluntarily (i.e. without being forced by court order). But, since it sounds like there are some possibly important questions of fact (as for instance if the landlord denies the tentativeness of your exit date), it will now depend on who the court chooses to believe. You can try a demand letter written either by you or a consulting real estate law specialist referencing the applicable statutory language. However, keep in mind that unless the landlord voluntarily pays you, the only way to force her at this late date is to file suit and see if your version is accepted. The problem with that is the result is not guaranteed and the loser can end up paying the prevailing party's court costs and attorney fees, if any. That's true of all litigation, but you recited some things that occurred that might go either way if tested. I would need to know more prior to advising you as to the odds of winning on this particular issue. You are on more solid ground regarding the failure of the landlord to account to you for the deposit and any portions withheld thirty days. See Chapter 90, the Oregon Landlord/Tenant Act. More is needed to be discussed. Still, if this one is tested in court, it initially sounds like the odds are relatively good in your favor. In any event, if the amount of money involved in all your claims is less than $10,000 and if you elect to proceed, perhaps consider taking action against the landlord in Small Claims Court. No attorneys are allowed there. All you might have at risk is your cost to file and serve. If you want to seek more money or if you are not comfortable with proceeding alone, contact a real estate law specialist located within 30 miles of your home. You might want to consult with such a specialist even if you elect to go in Small Claims Court. He or she can help you regarding what the pleadings should say and how to act at the hearing. Either way, good luck.