Is there an issue, Hashkafically or otherwise, with using a non-Jewish philosophical argument to defend the belief in Hashem or utility of religion without referencing the Torah? Like referencing Leo Tolstoy, Jordan Peterson, Anselm of Canterbury etc. as defenses of religion broadly beyond just pure faith and Emunah in Torah?
According to Rambam's Introduction to the Eight Chapters, it states:
Know, however, that the ideas presented in these chapters and in the following commentary are not of my own invention; neither did I think out the explanations contained therein, but I have gleaned them from the words of the wise occurring in the Midrashim, in the Talmud, and in other of their works, as well as from the words of the philosophers, ancient and recent, and also from the works of various authors, as one should accept the truth from whatever source it proceeds (ושמע האמת ממי שאמרו).
Hence, according to Rambam and his codification of halacha, there doesn't necessarily seem to be an issue with using non-Jewish philosophical arguments in order to defend Jewish beliefs. If anything, it might even be commendable, though there might still be details that one should be aware of and follow like nuances in halacha regarding the reading of idolatrous works (since according to Rambam, they'd be forbidden, though given the examples you gave, it should be fine if they're only pure philosophical/logical works. The nuances here are really a separate question but I still felt that it was important to mention since the content of the text you're reading and using is salient), but overall and in general, it is acceptable, at least according to Rambam's view.
I just also wanted to note that this interpretation of Rambam's statement is quoted by, and affirmed to mean what I wrote in this context, by Rabbis such as Rabbi Moshe Ben-Chaim in his writings, among others, and I am thus aligning myself to this authoritative interpetation.