How do I help my boyfriend cope?

My boyfriends Mom, is now in ICU with kidney failure and other on going health problems. Honestly, the doctors dont know what to think but say that she basically is doing very bad and is gravely ill...My boyfriend is very attatched to his mother, he is the typical "mamma's boy" overdone. How do I help him cope if , god forbid, his mothere were to pass away? He's already said if his mother passes away he would basically have nothing and he would go crazy. Years ago my boyfriend suffered the loss of a former girlfriend to a car accident, he told me it took him years to finally be able to function normally, he was binge drinking, never came home and dissappeared for days at a time...not wanting to live any more... He also has the tendency to shut people out when he is feeling depressed or stressed in anyway....My worst fear is this happening and our 5 year relationship falling to pieces. He wont come home, and basically feel that his life is over. How would I help my boyfriend if the worst were to happen?