You should check Mint again, things in the Linux world are improving fast lately. Some people got their grampas into Linux and they are happy using it, with your use case it can easily also be the case, the terminal it’s not needed, may be sporadically and to setup some things as you like at first, like changing settings to not enter passwords, may be it’s not so safe but it’s not as unsafe as using Windows. Just get used to the good habit of making regular backups. In any case just make a post asking and we will be happy to help. Just go ahead and slowly you will get confidence to do more difficult things. The freedom that you experience using Linux really worth it, but it can take time to appreciate.

If you use stock android and proprietary software, YES. Everything you type can be recorded before it’s encrypted.

Don’t fall into the illusion that you can have privacy with stock android. Google has admittedly igrored user settings to continue spying them.