If you could get the dealer to see the problem, you could try for a free transmission flush, just to be sure. I changed out my transfer and rear diff oils at 5,000 and both were black/brown. Can't wait to see what the transmission looks like at 50,000.
The FJ does have one of the most used Toyota transmissions out. It has gone through a few upgrades in the past years, and does look to be very well made. I see a lot of people killing FJ's, but have yet to see a transmission blow on a "young" truck... So my guess is your fine.
Defrost will make the motor change RPM when it kicks in, but I am sure you know that...
My FJ tranny took me a long time to get used to. It ain't no Blazer...
Try to find a user near you and try his/hers.
You near Wisconsin?