You can generate your own pubic/private key pairs to your hearts content.
Already flawed, pack up and go home.
Implementing AES means producing the precise ciphertext that the standard mandates for a given plaintext and key; we are talking about exact values, down to the last bit, so the language used to code the algorthm is irrelevant.
Firstly, StrongCoin is deployed to Heroku, you can read their security policy http://policy.heroku.com/security
StrongCoin is probably the least risky way to store and spend Bitcoins.