My poor Oscar!!! Pleez help ASAP

Question
He may die soon so I need help ASAP. I have a 30 gallon tank got 2 Oscars and a sucker fish. They only few months old and I'm getting a 100gallon soon because I know how big they get. A few days ago I noticed my black tiger Oscar is acting strange, kinda looks stressed. So we left them alone, stayed away. The next morning, he was laying flat on bottom, not normal. Tested water and my ammonia was sky-rocketed! it was about an 8! My tester at home didnt even read how high it was so I took to pet store and they told me the actual number.So we did 50% water change with distilled water, he said not to put any more chemicals in. Well it next day with leaving distilled water and still high ammonia. And now fish is swimming face down, tail up. and his body keeps floating up to surface and he is constantly swimming trying to stay in the water. He been swimming non-stop all last nite and this morning. I am going to use ammonia clear even though pet store said not to because they cant have high ammonia for any longer. He WILL die any time now. What do you think? Is he messed up permanently? Will he get better once ammonia fixed? Should he be put out of misery? I'm so attached to him and don't want to lose him! My other Oscar gets along great! they swim together all day long. and now he staring at him, watching him. Its sad he watching his friend die.

Answer
Put in the chemical formula you have to break down the ammonia, check your pH and hardness if the other Oscar is acting fine then these levels should be ok. Once the ammonia go away is in then watch for any changes, the reason why the pet store told you not to put in the chemical ie because of your sucker fish as they can react badly to it, but you must get the ammonia down or you risk total tank collapse, best of luck!