R David Sperling at yeshiva.co here addresses your question and brings a number of rejected opinions - to be clear the halacha remains that a Torah scroll does not count as a tenth in a minyan
In regards the question of using a Sefer Torah as the "tenth man" in a
minyan – yes this does have a vague hint of a source. Firstly, the
Talmud (Brachot 47b) ...
I always understood that, even if not forbidden and often seen, one should not touch the parchment with the yad to prevent erasing letters over time. I see R Hershel Schachter writes the same (Lesser Known Laws of Torah Reading, #54)
The Ba'al Keriah should not touch the Torah text with the tip of his
pointer, even for the purpose of keeping the place, ...