If it were me, I would just give it back and not expect and $ for it.
Do you know anyone with a salt-water tank? Maybe ask them to 'babysit'........??
As for amquel, here's some more detail as to why it won't work:
Although amquel helps remove ammonia, in this situation you'll just be delaying the inevitable. The cycle process needs the high levels of ammonia so that it can create nitrite and then nitrates... all of which are required for the cycle to go it's full course. By adding amquel (or any other water conditioner or additive) you'll just drastically slow this process down and your target of a 'fully cycled and ready to go system" back anywhere from a few weeks to a few months. As well you run the risk if creating other hicups.
So have patience and don't add anything until your system completes the cycle.
Well, now that I've said that I realize we have no clue what you're doing with your water. Can you tell us more about it? Is is pre-mixed water, tap, full of chlorine etc etc??? Give us this information and we'll be able to guide you through this cycle as best we can. Of course, this won't change the fact that IMO, you need to get rid of that fish.... even if it means you are giving it back to the place where you bought it, no charge.
Here's a link that describes the nitrogen cycle (ammonia to nitrite to nitrate etc). Obviously the link isn't specific to marine/salt-water aquariums, but the basic process is the same for all life (even humans!)....
http://www.physicalgeography.net/fundamentals/9s.html
good luck.