1. People eat for many reasons, sustenance being only one. People eat for enjoyment, because they're happy, because they're sad, to deal with stress, as a substitute for something else arguably more destructive and so on. The sooner you can adjust your mental view to treating food as nothing more than fuel, the better off you'll be;
2. American cities with their car addictions make it incredibly easy to lead a sedentary existence. Biking is a somewhat hazardous option that's not always realistic. The ideal exercise (in times of reward-for-effort) is probably walking. I live 7 minutes from work and the absolute minimum steps I could take in a day is probably 5000, maybe 6000 (I have a pedometer). 8000 is more common, which is still a bit low (10,000 is recommended). Live 10-15 minutes from work and walk to and from work every day and you massively better off;
3. People treat diets and, to a lesser extent, exercise regimes as a transitory effort to get back to some goal weight or fitness level, at which point they seek to return to the previous behaviour. This is a mistake. You're getting older. Your metabolism is, all other things being equal, slowing down (it requires more effort to keep it up at any rate). You should view a dietary change (in particular) as a lifestyle change, not a temporary adjustment;
4. Psychological addiction may not be as "obvious" as physiological addiction but its effects can be very real.
I'm sorry for your loss. It may sound callous but ultimately we are each responsible for our own well-being. If someone chose to die that way, it's sad but there's not much you could do. You have to choose to be helped.