This is a horrible situation, and I really do feel for you and your family. Like you said, no one anticipates such accidents happening or emergencies arising.
It sounds like you have 2 separate issues here, namely how to pay your current hospital bill and how to register your father for rehab. Let's start with the second, as it's easier...there is unfortunately no way for your father to qualify for Canadian rehab. You should start making plans for him to complete the rehab he needs in India, no matter how inconvenient or difficult it may be. rehab is essential for his recovery, and don't skip it.
As for the hospital bill, the good news for you is that this debt isn't transferable to you. So, if your father can't pay and has to leave the country, the government will have to write the amount off as a bad debt. It happens each year, and while its tragic for the system and the taxpayers of Canada, it is the way the system is designed. I am not advocating that anyone should try to abuse this system, but unfortunately such loopholes exist that allow people to get away with getting treatment and not paying for it.