I don't think barber college is an option for this guy. Do you honestly think any self-respecting barber college would take him with that mop of an excuse for a haircut?
Let me be serious for a moment, though. This guy needs to admit that he can't do the job anymore. Personally I'd LOVE to be back on the street, but I have had to admit to myself that I am no longer able. And while I can sympathize with the guy's weight battle (I'm more John Goodman than John Travolta myself) in his current condition he presents a danger to himself and his fellow officers. I mean, how can you count on this guy to back you up?
Dude, it's over. I know it blows, but you need to accept it and move on. It happens to all of us sooner or later.