This is a forum for technical matters, not legal advise, so my advise:
1 - No you can record audio. If the camera is on your property, viewing your property you can record pretty much what you like. Commercial properties are somewhat different.
2 - Dont know, not familiar with that kit. It looks like jonny 5 has got loose again.
3 - Again, not familiar.
4 - If he gave you a written quote listing audio as being included, then I would have thought sale of goods act to start with.