1A. Use two factor identification (2FA) to login to USAA or ANY account you wish to be super secure. USAA has the options to be offered. Use one of them that is convenient for you and can be accessed from wherever you are on the planet.
1. Use a Password Manager. Norton has a free one. I like Bitwarden. LastPass is a bit pricey.
2. Use internet security on your computers and phone. Again, I like Norton.
3. Change all your passwords NOW.
4. Contact any affected accounts of the suspicious activity.
5. Use a secure messageing on your phone like Signal. "Messenger" app on your phone is a little leaky.
6. Use an honest-to-God real end-to-end encrypted email account like ProtonMail. It's free and there are premium accounts, also.
5. I'm tired of responding. All of this is really basic info from last century.