Unfortunately, I wasn't near the printer when it clogged, so the I'm not sure on the exact failure mode. When I spotted that it had failed, the feed screw had stripped out the filament on the feed, so I can't confirm whether the stripped filament was as a consequence of the clog, or the clog was as a consequence of the stripped out filament.
The part was a very detailed model of a complete truck cab, and so yes, there may have been little bits of PVA each layer. As you say, its possible that the constant fluctuation in heat cycle for each layer, was enough to cause the material to burn slightly, and this could have contributed.
When removed the filament to try to resolve the issue, I did notice that about 50cm of filament leading into the bowden tube had become really brittle, with the section after this being the usual flexible PVA consistancy, so I'm not sure if this contributed. Unfortunately I binned this filament, so don't have it to hand any more.
Cura was used for slicing, so it should have reduced the nozzle temp as you suggested..