score:8
It depends on the terms and conditions of the airline you booked with, and your country's laws, but in general the most you will ever get back from an airline in a case like this is to allow you to cancel the flight and get a full refund. That's also the norm for major changes to a flight. Your description of the conversation so far sounds like that of an agent who knows he has to give you a full refund if you ask, but is trying to persuade you to keep on the flight.
If there is another flight that you could book and do what you want, then ask for a full refund and use the money to book that flight. Alternatively you could try to negotiate with the airline, telling them you are considering asking for a full refund, but you will stay on the flight if they make it worth your while. There is no telling how successful that might be - if there aren't many alternative flights then probably not very. However you might get some extra flyer miles, or a future travel voucher if you are lucky.
If it makes you feel better, you are a long way from the only person airlines do this to.
Upvote:2
First, the travel agent is your point of contact here. Any changes to the booking need to be negotiated with the agent; believe it or not, the airline has no control over your booking at this stage.
This is either very good, because the agent takes care of the leg work, in which case you should certainly patronize his or her services in the future. Alternatively, it is very bad, if the agent doesn't do anything and the airline will not assist you either. In the latter circumstance, you should not use this TA again.
Anyway, I think you are unlikely to get your hotel paid for because of a schedule change. Some airlines will do this (QR, EK, BA) but it is not something you can expect as a standard industry practise. [None of them will admit this in their Terms and Conditions though, they all insist it is a goodwill gesture. So no harm in asking.]
However, in my experience, the carrier is likely to be willing to allow you to take an earlier flight, as long as your stop remains under 24 hours. This should be at the same price, without a change fee applying. The carrier might also permit a change to route, but some carriers dislike doing this. Unfortunately, I don't remember ever having to deal with a schedule change on China Southern, so that is not from specific experience.
In your shoes, I would go to the TA and ask them to get you on the earlier flight, so you can at least enjoy the city.