Could be just a simple maintenance issue. With that sort of mileage on the car - I would definitely pull and read the plugs - see if they are excessively worn, any combustion issues with any of the cylinder(s). As for the jump in RPMs, that could be related to a clogged PCV valve, dirty throttle body (careful when cleaning, don't want to mess up the servo on the DBW TB unit), and/or vacuum leak. Common on 9th gen Corollas with the composite intake manifold - the silicon gasket between the manifold and the cylinder head could be damaged, causing a huge vacuum leak that usually manifests as uneven idle / idle surging.

Also possible that the AFR sensor is getting lazy or is faulty. Generally they hold up for a fairly long time, but they won't last forever. Some have died with less than 30K miles on them, others have exceeded 150K miles. They have to be backprobed with a scope to verify their signal waveform - but if you noticed that fuel economy took a huge nosedive, this would be higher on my list of possible culprits.