Previously Owned Ball Python

Question
Two weeks ago, I came into ownership of an 11 year old ball python. He was an old roommates who will not be able to care for him anymore, so I have given him a new home. Please bear with me, I have many questions. Firstly, everything I have read is saying to get him a larger tank! I'm working on it, but what can I do to keep him happy until then? He's only in a ten gallon aquarium and has no heat! The previous owner has also advised me to not heat the small tank, because he says it will overheat and harm him. Is this true?

Secondly, His previous owner has been feeding him three mice every three weeks. I spoke with the pet store attendant and they recommended one small rat, but the rats all seemed too large. Is he able to eat a rat? Which is best and how often. Also, how long does a ball python remain aggressive after feeding? He seemed a little nervous, but was very docile when I first picked him up two weeks ago, but since I fed him, he has been very aggressive. His head pops up every time somebody walks into the room and he just struck at my hand as I was trying to switch his water. Is this normal? It has been 6 days since I fed him.

Finally, he is also shedding. He has looked as if he were shedding since I got him two weeks ago. I would like to help him if possible. I was told it is good for them to soak in water, but with his aggressiveness, I have not tried it. Is soaking good for shedding snakes? Is there anything else I can do?

Sorry for so many questions. His previous owner has cared for him since he hatched 11 years ago, but in the past year, I fear Rush has been neglected. I would like to give him a nice habitat and a good home, but it is hard to find reliable information on the internet. I would appreciate any help you may have. Thanks.

Answer
WOW!  11 years in a 10 gallon...  I'd need to know exactly how big the snake is to answer specifics but I'll give you some general guidelines.

Cage needs to be at least 3/4 as long as the snake is.

Cage needs heat (but a 10 might be too small to heat).  New cage is a priority.  It doesn't have to be glass, you can use those plastic sweater boxes they sell at WalMart.  For $20 you can get a nice large cage.  Remember you need floor space not height.  Drill or melt 1/8th inch holes in it for air circulation.

Judge the prey based on the LARGEST part of the snake.  If the snake is as big around as a baseball at it's biggest point-it can eat something the size of a baseball.  

Snake should have a water vessel large enough for it to get into and soak-generally they will do it themsleves if they need to.  You just provide the vessel.

The aggression is probably just hunger.  And the bad practice of feeding in the cage in which he also lives probably isn't helping.