BSM Architecture

I have been reading thousands of pages of BSM documentation. I am having hard time connecting dots with regards to various components, especially BSM and OMi.   Can someone please answer the following questions. 

1) Can I install BSM SiteScope NNmi in an environment with out OMi?  If I do that how does Service Health data is going to consolidate events  and show HIs and KPIs .

2) If BSM and OMi are two seperate applications, why does BSM Database Guide lists "Event" database. How does data flows with in BSM  and which application owns events? Is that "Event" datatbase actually meant for OMi and I can skip it if I don't want to install Omi. 

3) Both BSM and OMi guides talk about data collectors and BSM collectors, for example you can connect sitescope to BSM or to OMI. What is the difference between doing it one way or the other. If BSM is not doing event correlation or consolidation why would I want to collect data in BSM? 

4) I can do most of the stuff in Omi like connecting to NNmi, Sitescope, I can create dashboards etc. The only things missing are BPM/RUM. Is there a standalone BPM installation, so I can just have a monitoring solution with out BSM( Opposite of what i am asking in #1 )