This showing that you have ammonia is proof that you have too many fish now for the biologic filtration you currently have. This is fixable however.
What size is your tank and sump, how many lbs of live rock and sand do you have in both the DT and sump. We can start with these.
There are many other parameters that you didn't mention calc, mag and PH
So exactly how are you working to get the ammonia down? Can you share a picture of your DT with us? I'd like to see how it's setup with rock and how your powerheads are setup as well. A skimmer would help you greatly with this large bio load.