I could go through a point by point rebuttal, but I'll just give a summary.
Exams are stressful. Unfortunately, so is life - a lot, lot more stressful, in fact. Best get used to it.
A Levels may in their current incarnation be glorified memory tests, but many university exams are not dissimilar. Since A Levels are taken primarily for the purpose of gaining admission to university, they serve their purpose adequately.
You seem to be incapable of understanding that an exam can be intrinsically difficult without being a memory test. I could easily write an exam paper for you where I give you the syllabus and 12 months to prepare for it, and make it open book, and in which you would still not be able to answer a single question.
Theoretical computer science degrees are not just 'basic programming, OS and hardware'. Lol. Has it ever occurred to you to wonder why the good computer science courses require A Level maths (and strongly recommend further maths) but don't require prior experience of programming? Are the professors who set the requirements just crazy? Hint: nope, it's because the courses aren't what you think they are.