Well, got the output of the recovery mode. For basically any image (even the stock 3.0.24 image that worked the first time), all proceeds normally until the flash write begins, and then we get:
Abort: image size larger than 1769472!
Flash write failed!
========Upgrade fail!========
Not sure what changed when attempting the openwrt flash on this device, but it now seems to think it can only handle an image of 1.7Mb...!
I tried to flash @RadioOperator's image from the bootloader prompt, but I couldn't get my arduino to TX. Probably because the arduino outputs 5v and not 3.3v
Decided to get a 3.3v usb-ttl adapter, will try with that..