1) Shorts generally mark you as a tourist, as Chinese do not wear shorts that frequently. Of course, you might already be marked as a tourist anyway.
2) Warranty problems, like is there one for US? Directions in what language? As moondog mentioned, knock-offs everywhere. They even have USB flash drives to work in a certain computer, but when you get home you find there is no accessable memory. Did I mention power and plug compatibility? Generally, better to stick to your home country for electronics.
3) Best advice I got, was to go to South Bund Soft-spinning Market and then look at the samples. When you find a suit you like, have them duplicate it in your size. I used Flora Zhang in 1F (1st Floor) No. 129. Nice fabric, decent quality, good price...under $100 for small size.
4) Can't help you with that.

Have a great time. Always carry bottled water to relieve the dry-throat syndrome from the pollution.