You are not really aware of the documentation are you?
ActionBar is not a community shim anymore, a compatibility library down to gingerbread is provided and supported by Google: http://developer.android.com/reference/android/support/v7/ap...
As RyanZAG explained, your multiple layout files should only re-organize fragments.
Yes Android dev is hard, with multiple versions, sizes, formats and bugs. But there is documentation, tools and example to adress them. Deal with it.
If you are willing to try again, as so many things have changed since Eclair, you can have a look at this exemple where you will see how you can use new API and a fallback when they are not available: http://code.google.com/p/android-protips-location/source/bro...