How secure is this method that I used?

Use a factory reset android telephone to access bitddress.org

Then use an offline browser on the telephone and open bitaddress.org (offline) and run brain wallet.

Type in an impossibly large and random alpha numerique code.

Generate address

Take a screenshot of the private key and public key using screenshot function on android phone.

Disconnect PC from the internet

Transfer screenshot from android phone to a brand new and encrypted sha-256 usb drive

Print out paper wallet and store in envelope

Take photo with a digital camera of paper wallet and store on SD card.

Delete screenshot on android phone.

Remove encrypted usb drive from PC before reconnecting to internet.

Store SD card, encrypted USB drive and paper wallet in safe places.