The oxygen sensor signal yada does not kick in until right after warmup. The trouble starting at about 10 minutes (= right after warmup), the reduced fuel economy and the code all emphatically point to the oxygen sensor. It is not unusual for the bad running to not exist at all times after warmup.
Check the sensor wiring. Otherwise, replace it. A new OEM (= Denso) O2 sensor costs only about $30 total through Amazon. See www.densoproducts.com
for the right Denso part number.