Mac – restore from a Time Machine backup without booting to the Recovery HD

The expected graphical settings are not provided from the recovery image, but you can find terminal in the Utilities folder and use ipconfig to set a manual IP address and net mask for any active interface.

ipconfig set en1 manual 192.168.3.1 255.255.255.0

As long as your Wi-Fi isn't connected, you should have a valid route, but you could also set a default route if needed using that command as well.

According to the Time Machine documentation it requires a HFS formatted drive to work.

To get around this problem, on my external FAT32 USB drive, I split it into two partitions. One for Time Machine, in HFS, and the rest for FAT32 to share files.

In you case, since it already has files, I would find a tool to shrink the existing partition, then create a new HFS one in the now free space and voila! Your problem is solved. If the existing filesystem is NTFS then Windows Vista and above I think will happily shrink it. If FAT32 then have a look here.