I'm using an offline computer for storage. Do you think it is worth moving all the files or maybe just the .dat file into a truecrypt drive or is that unnecessary and potentially could lead to glitches?
Yes you should. As suggested on the Electrum tutorial you should store all the electrum data on an encrypted folder. From Electrum website you can read: "I would advice a Debian installation with encrypted home folder for extra security." So if you choose to have a Linux with encrypted home folder it should be ok, if you use a folder (on Linux or another OS) without encryption the best would be to work in a TrueCrypt container.
There is no way that you get glitches or so, TrueCrypt is reliable. The most important with offline wallet is what you do with your backup seed. You should store it in a safe place. The safer is to memorize it and never write it down but imagine that for any reason you could not remember it or if you passed away (don't wish it of course) and you would to transfer your bitcoin to an inheritor the should have access to your seed to restore wallet. You have to think about many scenarios.
Another good training is to create a wallet (online or offline), transfert a few mBTC on it and then delete everything and figure out how to restore your wallet.