Sorry, this may be long but to understand the situation, I need to explain some of the dog's history.

Nibbler is 2 years old and has not been fixed. When Nibbler was about one, we took him to the vet for routine vaccinations. He got them, everything was fine, we took him home. 20 minutes later, Nibbler had cold-like symptoms. We took him back to the vet the same day, the vet said it was allergies. Long story short, the vaccination GAVE Nibbler distemper. A year later, Nibbler is alive and happy but "bounces constantly due to nerve damage from the disease. I have tried to get Nibbler neutered but I was told he needs to be in a full vet office under constant supervision due to the disease. I am too scared to take him to any vet because I feel like they may screw up again and kill him this time.

Lately, for maybe the past two weeks Nibbler and his "brother" Batman (adopted deaf and already neutered, also 2 years old, we think the man we got him from may have abused him) have been unusually bad. They have been peeing on clothes and DVDs and have been getting into the trash/jumping on tables for food even though they always have food and water readily available and chew sticks/toys when we are gone. Last night was the worst, Nibbler started a fight with Batman right infront of us (we could not figure out how the fight started) where they locked onto each others lips and we had to pull them apart and separate them. Most of this bad behavior happens when I am gone for SHORT periods of time, but not when I am at work for 8 hours. We take them potty first thing in the morning and first thing when we get home and then we have playtime until they get bored or tired. Nothing has changed recently.

Any ideas on what is going on and how I can attempt to fix it?

Are they crate trained? If not thats the first thing I would do with them.

Yes, they were crate trained when they were younger.

Try keeping them seperated and see how they do. Keep them on a leash in the house if you have to so you can keep them from fighting each other.