1. This conspiracy is only known by NASA and the other space agencies of the world, not the governments themselves. And not all the employees of NASA, just the upper echelon. I'm guessing in the early 60's they discovered that space flight is impossible, because without an atmosphere to help with lift, the thrust required to stay aloft and get to the moon was unatainable. Now they could admit this and put themselves out of work, or they could generate a charade that would allow them to continue to syphon billions of tax payers dollars from the government cophers. Also, they promised their dead president they'd walk on the moon before the end of the decade, and they certainly weren't going to let the impossible stand in their way.
Your uncle is using the information he has been given, it's just wrong. And you cannot see the curve of the earth from a plane.
2. I'm going to make the assumption you mean tides, not waves. And yes I don't think the tilting earth can be the cause of the tides. Particularly if the Earth is an infinite plane bisecting the Universe. The best explanation I've heard is that the UA which is propelling the Earth upwards is rotating underneath us, and that is causing the tides.
3. Again, there are not that many people that need to be in on the conspiracy.