You are correct that the Rating value is not a file metadata tag, but instead stored in the iTunes library database so any songs that are imported from a hard drive into another iTunes library database will no longer have the Rating info.
Home Sharing is designed to share libraries and enable dragging and dropping content to become a permanent part of another computer's iTunes library. Although that will preserve proprietary iTunes database info, Home Sharing is generally used on a local network within the same subnet and won't work across the Internet without a lot of additional configuration.
It is possible to use Home Sharing over a VPN, but the Windows VPN client doesn't support routing of the Bonjour service required for Home Sharing. There are workarounds for this and here are a few links describing the process:
iTunes library sharing over a VPNHow To Play Your iTunes Library Remotely Over a VPNI thought briefly about Apple's $25/year iTunes Match cloud service in lieu of Home Sharing, but I think it maintains its own ratings, play count, etc. and does not sync that info from your library.
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Edit: I assumed that your work PC was at a different physical location than your main rig computer, but re-reading your post, they may actually both be at home on the same local network and one is just called a "work" PC? If that's the case, Home Sharing only requires that each computer or iOS device be logged into the
same iTunes account. You are permitted up to 5 computers (not including iOS devices).
However if you copy newly tagged songs to another iTunes computer with Home Sharing, it will create duplicates if the songs already exist. The playlists themselves can't be dragged and copied between them, but you can create them with the same name (and rules for Smart Playlists) on the other computer.
You could always drag the newly tagged songs to the new iTunes library, then Show Duplicates and delete the older ones to keep the libraries in synch.
I'm not 100% sure of your exact needs, but I'm sure there is a methodology and routine to make it work. Maybe you could verify if the two computers are on your local network or not.
Steve