Rav Shach [author of the Avi Ezri].  To his way of thinking only Torah is Torah and nothing else. That means learning the Oral and Written Law and doing what the Law tells us. It is hard to argue with this. And he also seems to think learning books about the hashkafa (or world view) of Torah is a bad thing. He applies the verse in Ecclesiastes against making books to books about hashkafa. That is they are bad.
Now to a large degree it is true that most such books are amazingly stupid, and certainly take people away from Torah when they read that nonsense. [They make  obviously false presumptions or else have wolrd views opposed to Torah that they present as Torah and by that manage to pull naive people into things that are not Torah. ]

But what I am confused about is if it is possible to give Torah a slightly wider interpretation? And if so, how wide?

The first step for me is to look at my parents. What did they consider to be Torah? And also parents are the first place that the Torah itself give regarding orientation. Now starting from my own parents makes everything remarkably clear. They had a very definite idea of what constitutes Torah that is the exact same thing as Rav Shach. The Oral and Written Law. That means the Old Testament, the two Talmuds and the halakhic and aggadic midrashim;-- or collectively what is called "The Mesora."(Torat Kohanim, Sifra, Sifri, Tosephta, Midrash Raba, Tanchuma,  and the Mechilta.)
There still would be a wider idea of what Torah is about coming from the side of my parents than sitting in yeshiva and learning I think.
It is that grey area between Rav Shach and my parents that I find difficult to deal with. I think Rav Shach would have held that one should learn Torah all the time. My parents would have thought that a wide range of activities constitutes keeping the Torah like taking the family to the beach on weekends, learning Music, Math, Physics, Engineering. It is hard to know. Because the Torah itself puts parents first I would have to side with my parents, but I can see the importance of Rav Shach and of learning Torah --that is Gemara, Rashi, and Tosphot as much as possible,
[Looking at the Rambam and Saadia Geon it seems they were more towards the direction of my parents. The Rambam is famous [or infamous] for his approval of Aristotle and learning Physics and Metaphysics. The Rambam meant by "Metaphysics" not just the book of Aristotle by that name but also the works of Plato--as he calls it "what the Greeks called Metaphysics." That means a wider set of books than just Aristotle.]

I am being short on purpose. Today the world of Torah is not like it was in Rav Shach's time.  Nor is university like it was in my parent's time. The world has changed and so have the rules. In any case, we all need to learn Torah and also Math and Physics,-- and survival skills and an honest profession.
There is no difference of opinion about that. How we go about it will have to differ according to the person and situation.