Ok as an update, I figured out how to get this running in Steam. The problem was that EB is started with a command line on RomeTW.exe, and there was no way to put the shortcut the EB installation program creates into Steam (that I know of at least).

The solution is to manually enter the command line into the launch program button within Steam itself. In Steam, if you right click on the Rome: Total War launch button, there will be a properties option. In the general tab of properties there is a "Set launch options" button, which will bring up an empty text box. Manually type in "-mod:eb -show_err" (without apostrophe) into that box. Now when you run Rome: Total War, it will launch EB.

The downside is that I don't know a way to have a second Rome button in Steam, so if you wanted to play regular RTW you would have to go in and delete the command line. There might be a way to set it up where that is not necessary however.

Anyway, the mod runs and looks great, I am looking forward to trying it out, though I'm still relatively new at RTW. GJ to all who work on it.