The Init event of an Http Module is not guaranteed to be called once.  ASP.Net can and will spin up more than one application object if it needs to handle the Requests.

We had this problem in the core when the startup logic was switched to an Http Module, and had to move it back to Global.asax for that very reason.

The Application_Start event is the only thing that is guaranteed to be called once during the application startup, or you can use a static class initializer method that Joe described in his blog post mentioned earlier.

For the question about the EventQueue examples.  If you search in the core DNN class library for "EventQueue" you can find examples for how to implement it.

I used to have a walk-through on using the EventQueue, but I can't find that blog post here on DotNetNuke anymore.