05 2AZ-FE I4 is back spec'd to 0w20 by Toyota, so its official 0w20, 5w20, and 5w30 are all blessed. If you can run 0w20 without leaking and burning a bunch, give that a try. I can't I tried. Ran great, just leaked and consumed. But my engine is old and abused from prior owners. You should be ok
Its a 10k full synthetic, 5k syn-blend or dino engine. Subtract from 10k for driving conditions. "Lots of highway driving AND short trips" Is that 50/50 Highway city? Not much mileage for a 2005 so pls explain what you mean.
If you just converted to full synthetic 10k is a gradual move. 5k for 1st OCI, 7500 second OCI, 10k from there on.