Is it possible to change the watch diameter?

Yeah if you melt some more metal around it you can make it as big as you want

How do I set the smaller clock? Or is it fake?

Not fake. You need to rotate the bezel so that the large hands are going anticlockwise. Set the little time first, then set the large face time by only going in a clockwise direction.

I’ve heard conflicting information about this watch. Is it good at keeping the time and how durable is it?

Well I know it's a men's watch and being a petit woman it is bulky but I love the look and it works great after over a year. I don't wear it all the time but it never does me wrong. I get a lot of compliments on it as well. The sun and moon that move are gorgeous. To me it's worth the money

Is it possible to over wind the spring with the crown? The directions say to wind it 30 times before bed, that seems a little much if it was wound up

It is always possible to overwind manual-wind watches. Having said this, you only need to wind it once a day. I always wind mine in the morning after adjusting the time if necessary. You could start with 20 and see if that keeps the watch running through the night. If not go up 5 winds to 25. Repeat until it runs all night. BUT only wind ONCE a day to prevent overwinter ding.