As far as I can tell, uPlay allows you to re-download and install your purchased games as much as you wish.
Saying that, I'm pretty sure "account sharing" is against uPlay's ToS just like it is for practically everything else.
My saves appear to be stored in:
C:\Program Files (x86)\Ubisoft\Ubisoft Game Launcher\savegames\%cache_id%\46
Try playing the game to the first save point and overwrite it with your previous saves?
There was a point when I used to order something off them every couple weeks, but my purchases with them are getting fewer and far between.
I can't recall why I stopped favourite-ing them, but I stopped using them around the time...