I suggest running an engine flush/lube product for a short period. (Lubri-Moly, or even Marvel Mystery Oil, for 100 miles). After that, I would change your PCV again using the original Toyota version, even if it is pricey. I would change the oil again to a good brand in whatever weight the factory recommended, obviously full synthetic. Of course, a high-quality oil filter also... maybe even a Toyota filter. After doing that, you have essentially done your reset. Drive and monitor oil usage carefully.
I noted that your oil consumption went from a quart every 1,000 miles to a quart every 500 miles suddenly and concomitant with changing the PCV. My working theory is that your OEM PCV was getting old and causing some oil consumption. Then your mechanic replaced it with a completely defective, though new, unit - more than likely a Chinese product. At 160,000 miles on a well-kept toyota V6 that has had 5,000 mile changes, I would say you could have a little consumption based on wear... although that is unlikely. I would wager that doing as instructed will get you to a tolerable consumption rate of one quart per 2,500 miles. If that doesn't happen, the engine needs to see a mechanic. Assuredly, you cannot do nothing on a modern car consuming a quart every 500 miles.
Best wishes.
