I think we all need to be a little easier on Tom. Yes, he has made some fairly dire mistakes in setting up his tank. But chastising him isn't going to rectify the situation or encourage him to become a more knowledgeable aquarist. Instead we should be offering guidance, and solutions.
First off Tom, congrats on your new setup. It looks like a good and I can't wait to see how it progresses. Although I would like to address the issue of your ammonia. 4ppm is well over a safe amount, and is unnecessary to complete your cycle. Doing a fish-in cycle is a lot of work. You may want to return your tank inhabitants to the local fish store and continue with a fishless cycle. It's slot easier and faster than doing a fish-in cycle.
If you do intend to continue with your fish-in cycle you are going to need to do your best to maintain an ammonia level of 0ppm. I know this sounds counterintuitive because you need ammonia to grow nitrifying bacteria, but as long as there are fish in the tank. There will be enough ammonia to start a colony of bacteria.
If you are getting an ammonia reading of 4ppm after only 24 hours you are going to need to lighten you bioload by removing some of the inhabitants of the tank.
I'm a freshwater aquarist so I can't really comment on your stocking, but from what others have said it seems that your crab and puffer are not meant to be kept in a salt water tank. So they should be the first to go back to the store.
Personally I think your best option is to completely remove all inhabitants of the tank and do a fishless cycle. This will allow you time to research what you want to keep in your tank and what you will needs to do to make that happen. A fishless cycle is also a good time to work on your aquascape. It's a lot easier to play around with different aquascsping ideas when the tank isn't full of fish.
Good luck, and don't get discouraged just because you've hit a few road bumps.