I really empathise with you - I have a close young relative in prison for drug offences at this very moment.
Am I right in thinking you don't do much in the way of exercise?
Try to understand not only what you are doing to those around you, but what you are doing to your own mind & body, & decide to put those things to rights.
Simplest of all would be jogging, and/or you could for example go to a sports centre, maybe find there a personal trainer to help you get your body back in shape, if you could only start to feel fitter you might gain the self-confidence to continue & improve. You would also meet a different kind of person than you are probably mixing with now.
Get a bike and set yourself a modest target of so many miles a day increasing as you gain fitness. I can assure you that once you start to feel better your own self-respect which is probably pretty low will grow, success breeds success, you're only 50, decide now how you want to be by the time you're 55 & I'm sure it wont be back in prison (or even dead!).