This is clearly written from a western Christian view. It should be noted for completeness that the Eastern Orthodox Church still uses the Septuagint (in Greek speaking churches in the original, in others with suitable translations thereof; in English I like https://www.amazon.co.uk/Orthodox-Study-Bible-OE-Some-NKJV/d...).

I’d be curious to know if this difference in scriptural base also contributed to the great schism?

I think the schism happened for several reasons, none of which I can personally account. If people really want to dig in, the subreddit r/academicbiblical is full of well, academics and people who know their stuff.