First off thanks for a great tool!!
Had a small nagging query:
Can I safely use symbols like: ~ ` ! @ # $ % ^ & * ( ) _ + { } | [ ]\ / * - +
and also other advanced special characters like Æ Ç Ë Ì Ð § © µ ý (full list here http://symbolcodes.tlt.psu.edu/accents/codealt.html)
I want to use all the above special characters along with the mouse movement entropy to get a super secure key pair.
I will be putting all my life savings into it, so don't wanna take any chances. Would really appreciate if you clarify this nagging doubt!! Thanks.
Are you asking about the Paper Wallet tab? If so, for the BIP38 encryption, yes, you can use those specific special characters. And advanced ones the page is unicode. Please make sure any wallet you encrypt with BIP38 that you check on the Wallet Details tab to make sure you can decrypt it and that the Bitcoin Addresses match on both tabs. Make sure to print back up copies. Put the paper inside ziplock bags. Have a copy in a locked safe place.
Are you asking about the Brain Wallet tab? If so, then stop. Don't use a brain wallet to secure your life savings.
In general, you should spread your savings over more than 1 Bitcoin Address. You may want to spend a small portion later and it's safer to not put everything on 1 private key that you may later expose to a device that contains malware.
You might also want to read the FAQ on the Wallet Details tab "How do I make a wallet using dice?". Using physical randomness will get you the super secure key you truly desire.