Others are biting on the other topics so I'll just mention the genetics bit.
What about the claim that Native Americans are a lost tribe of Israelites, something proven false.
That's too big of an issue to get into here, but suffice it to say that your statement of the claim is an oversimplification (the original and current editions of the Book of Mormon state that the peoples of the Book are descended of Joseph of Egypt, and among the ancestors of Native Americans), and the 'evidence' that has been posited against is does not stand up to scrutiny.
Weren't the people described be Semitic? In that case there would be signs of Semitic DNA in the Native American population, if the genes have spread through the genepool then genetic drift won't eliminate all traces. And the things they describe aren't population bottlenecks, for a bottleneck you really have to reduce the population to a small portion of their overall numbers. If a Semitic population had been there for several centuries the DNA would have spread throughout North America. To wipe out that DNA you'd have to drive the Native American to the brink of actual extinction.
Apropos, the answers to all of your questions and the cure to your misconceptions are readily found on the internet. Whether the internet makes some people into atheists, I do not know, but one this is for sure: knowledge, even readily available knowledge, does not by itself make one more informed. One has to know how to seek it out, filter the truth from the noise, and then judiciously apply it.
It's not about knowledge it's about evaluating evidence and arguments. Mormonism isn't just claiming a couple Semites showed up in North America, it is claiming four major kingdoms surviving for almost 1000 years. The problem isn't that there aren't ways you can explain away the evidence, it's that every time there's a way to test the claims of Mormonism you end up having to explain something away.
Why couldn't the plates be investigated by an impartial authority, or the original text transcribed? Well the angel didn't want that.
Why does the little we've seen of the scrolls from book of Abraham have nothing to do with the described text of the book of Abraham? Well it was written by a Jew who wasn't writing proper Egyptian.
Why is there no evidence, genetic or archaeological, of these four huge middle eastern kingdoms that lasted a millenia or more? Apparently Moroni wasn't talking about the Native Americans after all.
Imagine that tomorrow someone discovered the book of Abraham scrolls hadn't been destroyed in fire, and were found intact in some forgotten collection, or some expedition on Cumorah found a bag containing some golden plates and the bag was carbon dated to the 1830s.
They items in question were then scanned and put online. My prediction is that the plates would turn out to be gibberish and the book of Abraham would have nothing to do with Joseph Smith's translation. What do you think the result would be?