It's a fair jump from physio to industrial chemistry. I work on the periphery of industrial petro chemicals industry and as far as I can see the best jobs in this industry are by technical guys with a flair for sales/business. The people in the lab do ok, but the ones who can talk the talk; both to buyers and on a serious technical level with engineers in large/important companies are the ones with who make the big bucks.
Clearly there is more to life than money and the labcoats could be ten times happier than the suits, but industrial chemistry is fairly specialised field and if he is doing a course as a "second best" it might make more sense to do something more general at this stage,which allows him to tailor his education as he figures out a real alternative to physio (or indeed an alternative route to physio). Its probably too late to change his course options now, but it might be worth considering his diploma/cert options (or UCAS if he applied) which could be more flexible. If he holds off to repeat, some of the last college places to be filled get adverstised in the papers and if I remember right, many of these tend to be science-related courses and might offer another option to him.
Best of luck to him and for what its worth, let him take his time; there's no panic. If he repeats, then in a worse case scenario, is he's back to a position similar to this, but a little older, wiser and more self-aware and probably better able to make a decision that is right for him.
Rebecca