you realy need a tree surgeon to look to see if its viable to keep or cut down and you mite want help if needed to cut it down . some trees like oak and boabab trees can be almost hollow wear cracks ofcourse can be the end of some trees . theres a famous boabab in africa that has a complete bar within its trunk that was dug out origionaly bye elephants .

Many trees have cracks in the bark. It normally does them no harm. They develop a callus over the softer interior and get on with it. Don't forget that the only living part of tree bark is a very thin layer under the bark and as long as that is still intact for part of the circumference of the tree then it will continue to grow and survive.