We don't have walmart here, but I can understand the guilt when you buy cheap from a large store. In college I always shopped at this struggling little store, but then a large supermarket opened up near them and I started shopping there. I felt like crap (even more so when the little shop closed down), but you've got to take care of yourself too.
Soon, he needs to understand first. He needs to see his end is inevitable, that all he can to is accept it, even embrace it. That sounded way more creepy than I meant it to.
Sorry to hear that. Sometimes you eat the bar and sometimes the bar eats you. I know that sounds like a random movie quote, but I think The Big Lebowski really summed it up better than I ever I could.