i didn't bother to read EVERY thread on here, but a thing to beware of with linux USB / live CDs: if your encryption requires high-quality random numbers, you might not want to generate random keys after booting from a USB boot / live CD; apparently that's not a good choice because the environment is more predictable. Anyone out there ever even take advantage of this flaw? I sure haven't; I've only had wikipedia entertain me with these thoughts

Honestly, it surely doesn't matter, but for those that love being paranoid: beware of generating keys after freshly booting from a live CD / USB.
As for creating a "100% secure wallet", I don't think it's possible to quantify or measure the % of security that a wallet is under. Keep in mind that your wallet isn't exactly secure if even YOU lose access to it! (It's no longer secure--it is useless!)