1. Although you do not state what type of fax you're using I'm assuming that it is something like the Express Modem Fax software. This software uses QuickDraw for imaging the fax, therefore it is only using the preview of the EPS file. If you save the EPS file without a preview then the fax would have no graphic at all.
The LW Pro 810 fax option will use the EPS data and send the fax in high resolution.
2. Yes, there is a phone book utility that comes with the LaserWriter 8.1.1f driver.
3. Windows users can use the all of the printer's features that make sense, for example it's unlikely that a Windows user would use LAT. Ethernet can be used but the Windows machine would have to have either TCP/IP or AppleTalk drivers installed.