I don't know... My older brother took the exact approach you just outlined with his SO, and he did it with more sincerity and compassion than anyone I know. She has a handful of illnesses and it has completely wrecked his life to the point that he might as well be dead. He isn't the person I grew up with. In a lot of ways, he already is dead, and it sucks really bad. He no longer is the compassionate person I knew. He doesn't have control of his own physical health anymore. He has no friends. It is a terrible situation. My point is that if it looks like beinf supportive is going to wreck your life too, maybe it's not worth it, especially when you're young.

Before everyone downvotes me and has a knee jerk reaction, consider that I have told you next to nothing of the entire situation, so you'll be responding to something you know nothing about.