1. Not quite sure what's going on there, but if you're connecting it directly to the PC, you'll need to set a static IP for your NIC card as well.
Example: NIC card with 192.168.0.7 as the IP, while the Xbox has an IP of 192.168.0.3.
2. I'm guessing you have a stock HDD? The C drive only contains the system files (dashboard) necessary for the Xbox to function properly. The saves are held on the E drive (I think in the UDATA folder?). With a stock drive, there is no F partition. If you happen to have the 10 GB HDD, you can format F to get an extra 2 GB of space.
As for your BIOS issue, the X2 5035 BIOS has Config Live, so you can change pretty much any BIOS setting through the supplied x2config.ini file. If you open it up in Notepad, you'll see something like:
; 255 characters max here, format is <drive>:<path_to_xbe>.xbe, e.g. "f:dashes\avalaunch.xbe"
dash1Name = c:avalaunch.xbe
dash2Name = c:evoxdash.xbe
dash3Name = c:unleashx.xbe
dash4Name = c:xbmc.xbe
dash5Name = c:xboxdash.xbe
As you can see, the first boot path by default is avalaunch.xbe. So, if you FTP into the Xbox, simply place your Avalaunch files into the C drive. Make sure to rename default.xbe to avalaunch.xbe. Reboot the Xbox and you should be presented with your Avalaunch dash.
Hope this helps.