To be quite honest, there's only one reason I don't believe in the FET and that's because I don't think a conspiracy of this scale would happen, its something that i would have to see to believe.
I am a little concerned that people like you do not see more reasons to accept that Earth is round.
Too many of our schools, in every country, fail to show what science is really about and let people learn that things are one way or another "because the experts say so". But science is really about giving everyone direct contact with evidence and with the process that made us reach these conclusions.
Lets see science of the most basic kind: we are sitting on an object (Earth) of an unknown shape, that is too big to see from any vantage point where a direct observation would be possible. What should we do?
First, we get reference points in which we can rely on. After a while, the stars seem the best option. Then we observe the stars from different places of the Earth and find that they do not move with respect to one another when we move around Earth. Now we have something we can do measures against. Now we have a way to measure something (Earth) that is too big to see in its entirety.
Navigators everywhere did the above since more than 600 years ago, and gave us what we need: every time you move 60 nautical miles North the stars move one degree South. This is a repeatable measurement that has worked flawlessly for centuries.
Now we can go back to the shape of the Earth: what shape of Earth fits the measurements?