Clutch hub nut: Good ol' 241 Red. Plan on heat to remove, I use red because if you EVER need to be there again it's a bad day already.

1) I forget exactly, battery draw IIRC? It's in here somewhere. Oddly it also swap the turn signal indicators from Black/Green to Green/Black.
2) I even fit a 44 on mine
3) Easy for me:) I did wrote an article on here about them.
4) Me too, but dang it was too much for me!
5) Ride it hard or soft, whatever. Don't let the V-twin torque make you forget they were built for RPM
6) The muffler is the thing on the bottom, the resonator is the thing that looks like a typical motorcycle exhaust. You can remove that whole resonator can, and the put "tips" on the dual exhaust outlets. Sounds amazing.
7) Shorai (OE) is still around and have supplied me with batteries even though they aren't listed anymore, BUT there's plenty of high quality Li-Ion batteries to find now! Just search by dimensions.

As long as it is motorcycle rated "JASO" and "V-twin specific" IMHO, I don't care if its synth, Dino, or a mix. 20w-50 should be fine for anything less than flogging it on a track, in Florida, in the summer, at 2pm, on a friday....;)

Or go all full cray-cray with APH:
https://www.youtube.com/shorts/a2lqBS2gSmk