The principle of multiple witnesses is very clear in the Bible and clearly exemplified in its accounts. So much of Moses' accounts is testified by multiple others there is no reason to doubt it when he gives a singular testimony as well.
A witness is someone who was
there, not just someone who says something. I can find millions of people who'll say that Smith found the golden plates, they're called Mormons. But that doesn't make them witnesses.
All stories I've read about Joseph Smith's finding of the golden tablets have him finding them alone.
You seem to be quibbling on the difference between saying they saw him find them, and saying that they saw them. Very well, eleven people, twelve if we count Smith himself, say the plates existed. Is it OK if I say they didn't, or should I believe?
As for character witnesses, if you believe the Pharisees and not Jesus, oh well. And if you believe Joseph Smith and not the many locals who had known him as a con man, oh well. That's your bad choice to make.
I'm just pointing out that it's not really dispositive, is it?