SBF: The argument ... relies on a few assumptions.
You left out at least one assumption and it's a big one: The God of the Bible exists. (Although I suppose you could say this is implicit in your first assumption).
It has become my belief that the evidence is overwhelming and conclusive: The God of the Bible does NOT exist. Therefore we need not worry about any "prophecies" coming true. Instead we should get on with our lives and work toward making this life and this world the best we can.
This is actually good news, and it's real. Good news.
Consider for a moment Richard Dawkins description of the “The God of the Old Testament [who] is arguably the most unpleasant character in all fiction: jealous and proud of it; a petty, unjust, unforgiving control-freak; a vindictive, bloodthirsty ethnic cleanser; a misogynistic, homophobic, racist, infanticidal, genocidal, filicidal, pestilential, megalomaniacal, sadomasochistic, capriciously malevolent bully.”
Although there is no objective evidence to support the counterfactual assertion that the God of the Bible is real and actually exists, there are in fact plenty of scriptural proof-texts to support Dawkins' assessment. If you've been a JW for any length of time you probably know most, if not all, of them. Good thing it's all fiction.
Ponder that and it's ramifications!