The first issue will be fixed in the final 3.0 release.
Concerning the asynchronous issue, from 2.3 onwards, only the visible folders/documents are initially loaded. Then the folders are loaded when they becomes visible.
This should fix your issue. Nevertheless this KML sample displays information depending on the time.
For the moment, the SL KML layers are not timeaware and thus the information is not filtered by the time.
We are considering to add this functionality in 3.0 final.