1. For Top 50, your score is based on when you submit, but the deck that the computer will play in the Top 50 is the one that you currently have equipped after the game saves.
2. The huge scores (above 300k) are hackers. Jmizzle7, as far as I know (I haven't checked the scores lately) has the highest legitimate score.
3. Fate Egg can be useful, but because of it's randomness, it's pretty much a useless card in the metagame.
4. 70 HP for animated Titan IS correct.
5. There are plenty of decks on this forum that are great speed decks for PvP. I'm in class right now, so I can't link you, but check the Mono- and Duo-Decks sections. Speed Poison, Mono-Dark, and Mono-Fire seem to be the most common.
EDIT: Ninja'd by Chris. >.<"