You're not going to hell. If you are then the rest of us are because I just can't see any reason why you would. As for being a failed Christian I disagree. If you believe in God (which you do) and you're basically a good person (which you are) you'll be fine.
imho your obsession isn't stupid. I get freaked out when I think about death too. I'm dealing with it better than I used to (after I had my kids I got a lot better with that stuff). But what you're feeling isn't stupid at all. So you're worried? Yes. Nutjob? No no no.