My home button does not push in

if the front is coming away from the rear case then the home button will not be able to make contact with the logicboard. You need to open the ipod fully and find the cause of the swelling..perhaps it has been dropped and split the seal, or more unlikely the battery is swelling and pushing the display up. Either way opening the device and repairing the problem is the only solution here-you shouldn't need a new home button, it will work again once the front is secured to the rear.