Not the original commenter nor an electrician, but I did plenty of reading of the requirements here in Quebec before installing my Tesla charger with my electrician father-in-law. From my understanding: attic and wall absolutely count as dry environments, NMD is ok for those. Not sure why you need a junction box before going outside though.
About stripping the neutral wire before going into a conduit, I found this: "installing stripped Romex where the wire may be susceptible to damage is prohibited. This may include installation near sewage lines, bins, garage doors, and even those attached to the face of concrete walls!". Looks like it's ok to strip before going into a conduit, as long as the conduit protects well from environment, from external physical damage (animals, shovels) and is well waterproof (directly connecting to the charger or in a waterproof box).
You could also try to find a 6-2 wire, even better a NMWU so to avoid using a conduit and staying flexible, but those are pretty hard to find.

About the 40amp breaker, I know my Tesla model 3 can only take 32Amp so I kept my 8-3 with 40Amp breaker. Model Ys and some other cars can go a bit higher, but the charger can be configured to stay below 40Amps. If your charger doesn't go beyond 40 or you car use 32amp for example, no need to upgrade the breaker, but it's nice to have it easily upgradable when faster charging becomes available (e.g. your next car).

Anyways, just wanted to participate in the conversation, better have confirmation by a pro. Congrats on your EV, they are so much fun!