Tough one on the GCSEs, bottom line pretty much all kids try to have a strong personal statement. Work experience can be helpful.
University Places are offered based on predicted grades and also clearly performance at gcse, and yes, someone with ten As is a better performer on paper than someone with seven.
However, as my daughter has just went through the application process a year or so ago, each uni has different entrance levels, so some require three As at a level. Others an A and two bs, it depends on the uni and how "good " they are i.e. A Russel group uni will have stricter entrance requirements than a non Russel group.
Offers tend to be conditional and then they are made unconditional the day the a level results come in, so he will get a place.
I would say of my daughters friends and my friends kids, maths is the one a level that seems to cause the most problems, it's a very hard subject, and even kids with an A star at gcse have struggled to get anything close at a level and it has cost them the uni place of their choice and ended up at different unis via clearance. Nearly all thought doing maths was a mistake unless it was something they loved. How does he like math? If he thinks it's going to be tough, drop it now.
There is so much pressure on kids now, it's awful,