Harrison
I've watched your P-40 with great interest and I've witnessed your skills evolve over this very short period of time. As with most people here I will be watching this build too. It looks like a cool subject to model.
Just a suggestion, don't go to crazy with the details on the cockpit just yet. You still need to practice all that you've been learning on the P-40 build.
As for your questions, Not seeing a photo I can't comment on the color you are refering to.
To the best of my knowledge the seats would be the same as the rest of the cockpit but I would defer to the more knowledgeable people here
Question 3, Are you using Model Master RLM 66? If so this is very dark so in order to see the details you could go with black or in my opinion a gray. Something to make it stand out from the walls and then whatever color you choose do a dry-brush to make it pop.
Good luck my friend