If you go to whatismyipaddress.com, is the IP address you see there the same your router tells you as your WAN or public address?

And if it is different, is your routers public address somewhere between 100.64.0.0 and 100.127.255.255?

Yes it is possible and absolutely viable as a starting point. You might will start experience some drawbacks of hosting on a Windows desktop system more sooner than later. Reboots due to system updates as example.

Use it, and think about getting an use office PC that can hold your drives.

A pile of shame, consisting of all the books I bought and haven’t read yet.