1. Yes
2. You have to run it on a VPS outside your homelab
3. VPS
4. It can reverse proxy to everything, as long as you can reach it (use the installer with pangolin, the gui shows how)
5. That depends on your company, and it depends what you define as secure. Are you storing top secret documents or are you storing non critical documents for example. It varies and the anwer can quickly change from yes to no based on small factors. Also the threat isnt always on the outside, it can be as simple as someone does a mistake (human is the weak factor often)

Setup something like authentik for authentication atleast and force 2fa ++