1.  Yes, I have been to several zoos in different cities. Some of them were big and the animals had enought space there but some were too small to keep animals there.
2.  I think, it depends on the zoo. If it is a good one, definitely it is worth visiting to see animals closer and to be more empathetic to them in the future.
3.  People can see a large variety of animals. In Saint-Petersburg we have lions, monkeys, polar bears, giraffes and many more species.
4.  The endagered species can be saved in the zoos because in zoos animals are well fed and their health is under control. Animals can breed in the zoos and their offspring mostly survive.
5.  Surely, keeping animals in small cages is a crime. Though, not all zoos can afford enough space for their animals. I think, the minimal size of the cage should be regulated by government.