As long as the white patches aren't fuzzy, there's nothing to worry about. I have fish that do that, and are perfectly healthy.
You really should upgrade your tank, like you mentioned yourself. Don't stress too much, he looks perfectly healthy. If he's in a half gallon though, you'll want to change that 100% daily, especially if it's unfiltered. You need to get a heater.
Now, the slime hanging from him would concern me. It could be Slime Coat Disease, or could just be shedding it. When reading the symptoms and comparing though, it doesn't sound like it. He probably just picked it up, or is shedding it.
Just upgrade to a 2.5g or more with a heater ASAP.
You really should upgrade your tank, like you mentioned yourself. Don't stress too much, he looks perfectly healthy. If he's in a half gallon though, you'll want to change that 100% daily, especially if it's unfiltered. You need to get a heater.
Now, the slime hanging from him would concern me. It could be Slime Coat Disease, or could just be shedding it. When reading the symptoms and comparing though, it doesn't sound like it. He probably just picked it up, or is shedding it.
Just upgrade to a 2.5g or more with a heater ASAP.