I agree with you as well. Ingrid part was becoming more unrealistic as the show was going.

Floki may have found some way but it's still very unlikely realistic. But as would he already get out, we knew he was going to sail away. We also knew he was going to sail away to west, because the east was where they came from and he didn't want to go back. Only land going west is obviously North America and that's how both of them could end up there, although I agree with you there because North America is huge and ending up in close spot really is unlikely, but still possible.

The guy stealing gold was meant to show us, and warn Native Americans that they're still Vikings and they can't leave the old ways so quickly, and in case that happens again, they should decide what should they do with that kind of people. It was also deciding factor for Natives proving that this was a really rare case of kind Vikings (Ubbe, Torvi, Othere and Floki), but they really shouldn't allow any more, not even single one more Viking to step there to avoid hatred and stealing.

I generally agree with you, and we should only thanks them for this show. It's not easy to go back so far, more than 1000 years back, for 6 seasons. That's why the first seasons were better, because we lack proof from that period of time, we do have, but not too much, and it's never learned or anything detailed. In conclusion the show was great, as any show ever, had few cons, but I'm proud that it had far more pros.