Yes it can.
I said Josephus's passage on Christ is believed to be a pious forgery. Many scholars (with some good arguments) believe that the statement was forged by well-meaning Christians.
What you said is that you can’t disprove someone is a prophet — I say you can with very little work in Joseph Smith’s case.
No; what I said is that Mormonism is a matter of faith, and faith can't really be disproved. At best, you can challenge assumptions and expose internal inconsistencies - but those are generally convincing only to those already convinced of your own presuppositions.
Yes it can.
Why can’t faith be disproved? If someone has faith in a prophet and it is demonstrated that a prophecy is false, then their faith is contrary to reason. Disproved.
As far as the claim that the history of Josephus is a forgery, Josephus was known and appears in other documents external to his own writings, but taking you on your own terms, show me even an arguably credible contemporary history by an American Indian/Lost Tribe from Judah talking about Christ in the Americas. Or lost tribes of Jews in the Americas. The two faiths are not even comparable. The Mormon faith runs contrary to reason and evidence. The Christian faith is consistent with reason.