1. Go to Tools > Options > Saving & change days to keep incompletes from 7 days to 9999. Also beware of the Clear Inactive button next to the explore button at the bottom of LW's interface.

2. To restart them, go to Library window, select incomplete folder, then select all files within, press Resume button. They WILL restart from % they were but ONLY after they have started to download again. In the meantime they will show 0% so ignore that figure .. it's misleading.