Hi Bertie, I just wondered how you got on with this since you didn't get the help you were asking for. I can't play it or I'd oblige. However, I thought a couple of things might be useful.
I'm not sure what your problem was with identifying the notes from the key signature plus any accidentals. There are pretty solid rules to apply, so it should just be a matter of taking care to apply them (unless you think there may be an error in the edition).
For slowing down recordings so you can catch details, I expect you've tried the speed control on YouTube etc., but if you're anything like me the distortion caused by this makes it harder to hear tones. What you can do, though, is use an audio app that doesn't just chop up the data, but properly resamples it. I think Audacity will do this. It takes some time to process a section, but then it sounds fine slowed down. It's a while since I did it, but I think I'm right in saying Audacity does it. I'm on my phone traveling just now or I'd check.
Of course, you might have this all sorted by now, but it's a technique that might help another time. It looks quite a challenge, that piece. Good luck.