OK, so I preheated, took the filament out, cooled down, took the fan housing off, took the hotend off (left all the wires connected), took the nozzle off, heated to let any plastic in there to drip out; nothing dripped out, but I scraped around in there with one of the small allens and got some bits of plastic out, used the pointy end of the sidecutters to get some of the hard plastic out of the noozle.

Then the ptfe tube had free passage all the way through the hotend. I inserted it halfway down the noozle threads, threaded the noozle, then screwed in the tube-holding-thingie on the top. Then I screwed the noozle in all the way, letting it push the tube up, and periodically releasing pressure with the above holding-thingie (what's that called?)

It made things a little better maybe, but didn't instantly transform it back to like new. I reprinted a half-hour part I've been working on, 100% infill ABS because the instructions say this part is the critical piece that needs to be strong. Last time I printed it, all the threads on the sidewalls didn't adhere to each other, so it was like horizontal hairy curtains all around that came off. This time there's still some hairyness, not as extreme.