I have the workshop manual so that should help.
One thing not mentioned so far is belt tension. If the bike has been worked in the past by a HD dealer for recalls they will have set the belt far too tight. And that could be what caused the pulley spline wear if it wasn't rectified. Ages ago, my M2 had recalls done at the old Chester HD shop and they set the belt tension like a bow string. I loosened it as soon as I realised. While you're at it, check rear wheel bearings for wear too.
I read about that a decade ago and have ensured that its not overly tight. Good call on the rear wheel bearings too thanks.
Your neutral switch has done you a massive failure by failing.... and thereby allowing you to discover this worn pulley whilst you're in the comfort of your workshop.
You have no idea how delighted I am to discover it before it became a roadside epic and garage cursefest!
The big nut came off this morniing without any drama - seems not to have been fully tightened. There was loctite on it and the locking plate screws too, but not tightened sufficiently.
As far as I can see the output shaft splines are not damaged much (if at all) but the sprocket is toast and very chewed up. I'm guessing the sprocket material is softer than the output shaft.
What's your experienced opinion of the output shaft teeth, pics enclosed?