You can either get a 4G / 5G outdoor antenna or change your mobile provider hoping it’s better than the old one.

Otherwise, there isn’t much you can do.

This isn’t always the answer. There are people who need to use macOS because, e.g., they need to build macOS apps. Even simple building tools such as Python’s setuptools or py2app requires you to be on Mac in order to build for Mac.

It’s overkill. Here where I live, only businesses invest in that much. Most users are happy with 150-250mbps.

What are your devices? If you have Apple only, Books already does everything you need, and you need no self-hosting.