I have completely stopped using google services and software on my personal devices (even have lineageos + microg on my phone. The problem is that I can't just explain to the technically uneducated people that I changed mail providers. How should I go about doing this?
While you're at this, get yourself your own domain so should you ever want to move provider again you don't have to change your mail address again and can just point the new provider to the same domain
Theoretically yes, but it is probably not a good idea to use it for email since duckdns might not exist in a few years meaning you cannot log into services that used that email.
No. You don't own that. Plus you need direct control over DNS records since you need to set up MX and TXT records and I think some other records as well.