As I read it, he was 23 when he left the RAF and was not a pilot. He's gained a PPL in the last few years and now wants to fly professionally?
He won't get snapped up as he doesn't appear to be an ex-military pilot. Big difference.
Command in 5 years after training (so around 50 or so) is possible but it's not a guarantee. To be promoted you first need a job. Also, you need to pass the course, not every one does.
The work pattern described sounds suspiciously like Ryanair and historically, they rarely take over 40yo.
To get it all done in 18 months will take an enormous sacrifice, if on a full time course, he's looking at circa £120K in costs.