SingaSong, don't worry. Medicine applications are really complicated, and 60% of those who apply wont get places. A 4xA* prediction will not be enough if you don't ace the aptitude tests or have bags of vounteering and other experience.
A whole (expensive) industry has grown up around helping kids apply for medicine and some schools are clearly a lot more experienced than others. (A quick Google suggest at least a dozen suppliers and that is not including private sixth forms who boast of their medical school success rates.) As a result it is perfectly possible for a child to be good enough for a place, but not as good as their competitors simply because they have not understood the tactics needed.
DD had been very ill leading up to her submitting her UCAS form. She had missed open days and writing her PS and getting into school on a daily basis were challenges enough. So by default I ended up doing the desk research (with some great help from members of this forum) which allowed her to make informed choices. But her choice. For example I suggested if she really wanted a place the odds were probably best at Belfast, but she wanted to have a crack at Bristol, even if it meant no place and having to reapply the following year.
Like OPs son, there were a limited number of med schools where DD stood a good chance of interview, and which met her criteria (no PBL, city campus). But by knowing this, and understanding that it is all about points and scoring, she picked up three interviews and two places from her four applications.
These kids are only 17. Yr 13 is really busy. However it is their life. They have to own their PS, they have to get the grades, they have do the volunteering, they turn up for interview, they need to decide on subject and University. However parents have a role as mentors and good mentors ought to be informed. (And there is a steer learning curve if you don't have medicine in the family.)
FWIW DD did manage one open day, where she claims she was the only one there on her own, that one child turned up with 17 family members, and that only dads asked questions, with the med school seemingly gearing their presentation towards parents. (She did not apply there!) She is now careful not to say she will be reading medicine, unless specifically asked about subject. Despite all the moaning there is something very strange about the reaction to "becoming a doctor", even within parts of our extended family. Reading medicine is something she wanted to do, but clearly for some it carries a unique status, and with it sometimes, a burden of family expectation.