Oh goodness!
ya, doing regular water changes, getting rid of the bio balls and pulling some rubble in that space should help a ton!
But dont remove the bioballs at one once. Take out a handful every week. You want to let the bacteria living in the tank to increase, to make up for what you remove when you take out the bioballs.
And i wouldnt worry too much, i think sharkie ( a member on here, had her eel go for a month without eating).
Also cycling the tank means that you allow for the bacteria population that will process the fish waste to grow. So when you replace that much water, it can kill off that bacteria and the tank has to recycle. When a tank is cycling you have ammonia and nitrites present, which are very toxic to living things. Thats why you never want to cycle with live animals.
Also that large of a parameter swing when doing a large water change can be very stress to the live stock, which is also why you never want to do large water changes like that.
But now you know! Glad he made it through! Can we see some pics? I bet he a pretty pretty fish!