Hi RedRover57,
Just finished part 10, where I decided to upgrade LS to rifles before attacking American cities following your advice no. 1)
As per 2), I do not care even if I sell conquered capitals, specially if they do not have really good wonders. Considering non-existant trade routes selling them looks even more attractive option
As per 3) I agree, I will be behind in tech. This will probably be my bigger burden though the whole game. Going for tall, science focused cities could compensate it a bit.