Cedar is TOXIC to ball pythons, not to mention lots of other small animals. If the audible breathing persists, take the snake to a QUALIFIED reptile vet.
I would try not feeding the snake hamsters. Try rats or mice first and see if he will eat them. A ball python can eat a prey item that is as thick as the snakes widest part. Don't worry, his jaw will unhinge and his neck will stretch to allow the prey to pass through.
Also, a 90g tank is meant for fish, not reptiles. Get him in something smaller, a plastic 32qt tub would probably be your best option. Also make sure whatever heat source you are using has a thermostat to control how much heat comes out of it. Otherwise you risk cooking your snake.