Here is a non sectarian Biblical Archeology Site that looks at the DSS and the MT. Again, there is as the site knows a “relative stability” of the MT, but it does show that the MT is not entirely in agreement with the DSS.
Like I said, I think the evidence now suggests that the MT comes from 1 mainstream Hebrew Textual tradition but that there were other textual traditions in Jewish circles, also mainstream, from where the LXX came from. I think scholars have called this one an Alexandrian-Hebrew textual tradition.
Here is another article from Biblical Archaeology, which again shows evidence for a Hebrew translation from which the LXX was translated, one that is likely different from which the MT was translated.
Why haven't the Catholics ADMITTED that THEY have removed the VERY BEST Scriptures from the BIBLE???