Perils of time travel

Little Stink and Stink just finished watching "Meet the Robinsons" for the umpteenth time today, and I got to thinking.
*Spoiler Warning* The following may contains spoilers: While this movie has been out for a time now, there may be some of you who haven't seen it yet. On the off chance that you're still wanting to watch it, but haven't gotten to that point yet (under a rock, without electricity, transportation and or tied up in a basement forced to listen to Rush Limbaugh and Glen Beck alternately... poor bastard) then STOP READING! You've been warned.

So, in the movie, this kid, Louis, finds out that his own son from the future has come back in time to make sure certain events happen as they're supposed to. In the process, Louis finds out a lot about himself, including what his family is going to look like.
This of course raises some questions:

1. Since Louis looks a lot like his future self, only younger, why the hell does his future family not notice it earlier? I know that wearing a fruit hat might make a small difference, but not that much. Reminds me of a cartoon that I saw once, where Superman was flying around with glasses on. The caption read "Confusion ensued today as no one was sure if it was Superman disguised as Clark Kent, or Clark Kent disguised as Superman."
2. When Louis goes to the future, he discovers all of these inventions that he will make. Doesn't that sort of preclude him discovering them in the first place? A perfect example of this is when Louis and his son, Wilbur, are discussing the invention of the time machine. Wilbur explains that his father had woken up one night with the idea for the machine, and they go through the subsequent incarnations (or what's left of them). Now, Louis knows he's going to invent the time machine before he dreams it, therefore rendering the earlier statement false.
3. I don't know why, but for some reason, I have an easier time of believing singing, talking frogs over a (semi-intelligible) talking dinosaur. Not really an issue with consistency, more of a personal observation.
4. There is no point 4.
5. At one point Louis is talking to the villain (an evil bowler hat.... don't ask) and says, "I will never invent you". At that point, the villain turns to dust and the future is saved. three cheers... whoopee... Are words really that powerful? I have yet to run across any future inventions or relations or anything like that, but honestly, I would be afraid of what I was saying. You could get a warped butterfly type effect just by saying the wrong word to the right person.
6. What's to say that someone from Wilbur's future doesn't come back from the far future to fix something that Louis had to fix when Wilbur was a kid? What if Doris needs to be prevented from not being invented to stave off some interstellar invasion of self-conscious bald men?

Y'know, it's questions like this that have kept me from conquering the world.