Flat Earth was designed to make Conspiracy Theorists look like idiots, but too many of them started brushing it off too quickly. They learned their lesson. Birds Aren't Real was designed for the same purpose, but was deliberately made to be ridiculous.
Add to or poke holes in this theory.
Correct. The only civilisation that thinks the world is round is us. They even teached that schools till 1920/30. All previous civ's knew it was flat.
Actually, this is an american myth created by the author of the legend of sleepy hollow in the 19th century! Virtually all educated since ancient greece all learned that the world was spherical.
In any case, It sounds like you may have an interest in the subject! Please join us (and engage!) on the community I created specifically to explore/discuss it and share your views and experience!
Please click my username and on the right hand sidebar under "Moderator for..." will be the link. It doesn't show on small screens / phones, so let me know if you don't see it and I'll pm you.