Yes, additional seat selection fees apply since TN is not in OW.
Probably, I can get upwards of 2 or 3 cpm, but that is for business redemptions. You are getting more than 1cpm though, since seat selection fees will be charged either way, so it's not the biggest waste.
Personally I would pay cash and save the miles for an aspirational award, but I don't know what your finances look like, so if you could do with the extra $350 in the bank, use miles.
In your opinion is it fair value to book this flight with miles if I am not planning to book flights with AA or their partners again? I'm looking at it more on a financial angle vs future travel angle.