When exactly did you create your wallet?
Myrnyi is not the OP. Kittn2 is and your question should be directed to him.
I store my seed in txt flle as well, and this file is in my phone, and noone can read it (except me). It's very easy... I have packed the file in 7zip with a password, the password is more than 20 characters long.
Besides the things that o_e_l_e_o mentioned, I assume you are aware of keyloggers and fake keyboard software that can record every touch you make on your phone which also includes the decryption password. You are also giving permissions to all kinds of software to access your memory, pictures, messages, camera... Can you trust all of that?
I encrypted my file a few years ago on my linux debian computer, I do not use this comp now. I have only this encrypted file in my phone and in two usb sticks that are in a metal safe, and I have learnt my seed by heart. Everything else is paranoia...
In that case, why do you also need a digital copy of your seed (even if its password-protected) on your phone. Your memory will weaken with age, sickness, or due to an accident. USB drives can fail and corrupt data with time. Have you ever checked if the USBs still hold what they once did?