I agree that he was not being deliberately self-destructive. I don’t think that the problem was eating food that was past its sell-by date though. Frozen cooked chicken can be safely eaten decades past the sell-by date.
I totally agree with you that the root problem is that he’s homeless. I have reworked this section to make my intention clearer. Again, I had not anticipated an interpretation like you have presented. Thank you for sharing it.