Just want to clarify: Did you install CSSU and have you checked "Perfect setup for N900" instructions? CSSU uses the stock appmanager (at least so I have understood). And I downloaded from wayback machine pages the flasher and the image. There are here also instructions to get Netsurf 3.8 browser working through easy debian (which I suggest you install on an sdcard ext3 formatted). And cutetube2 has also instruction for power kernel to watch youtube or to download videos to the N900.