Can I set up and use DSL Verizon on OS9 without using it's requirement for OSX? My old (but updated) Mac won't take OSX without extreme sacrifice.

There's no reason why it shouldn't work, it's the setting-up process that might cause problems. Frequently, ISPs will use an automated setup program that configures your computer's network settings. Verizon may have one that only works on OS X. You might first try calling their tech support number and asking if they can talk you through setting it up manually. The relevant settings are in the TCP/IP control panel. Otherwise, If you have a copy of OS X, you might try temporarily booting into X, running their setup software, and then copying the settings from the OS X System Preferences - Network panel to their equivalents in the OS 9 TCP/IP control panel.