Skywave,
The amonia will build up quickly until the nitrosanoma and nitrobacter bacteria communities develop.
Amonia will be fisrt, it will drop, next watch the nitrates, then it will fall and finally the nitrates will raise a little but go back down as the bacteria communities grow. That is one reason for turning of the UV. You don't want to kill bacteria right now.
With this much filtration and adding more biomedia along with the NH3 removal chemical, I think you may loose a few more fish but it should stabilize quickly. I would reduce your feed to every 2 days.
