UPDATE, Day 3: it finally came off! My daughter and I seemed to have muscled some play into the gap enough for me to get the edge of a flat head screwdriver in there and lever the thing off. I think the Blaster I put on had some time to soak in and loosen the crud. I cleaned everything out and put a layer of Phil Wood bearing grease. Everything is running smooth now without the need to buy a new tool. Thanks to all for your suggestions!
...I need your help. This is the hub for my wheelchair wheel. The quick release is stuck on, and the only way I think I can get it loose is to unscrew the axle sleeve from the camber bar, thereby gaining access to the interior so I can unstick it. I’d use an adjustable wrench, but the surfaces (on the right, flush with the inside of the hub) are underneath the flange of the hub. Is there some variety of basin wrench or something that can get in there to unscrew the thing?