Can you use fructose in place of sugar in baking?

Yep. Like stated above, use slightly less. Be aware that fructose does not crystallize in the same way that sugar does. For biscotti, this doesn't matter one bit, but things like meringues and other concoctions that require the sugar to crystallize might fall flat. Enjoy!

For biscotti you'll be fine. Be aware that they might not brown as nicely.

I think so. It is sweeter than sugar so only use 2/3 the amount called for. It may affect the final texture to some degree, but for biscotti I think it'll be fine. http://www.foodsubs.com/Sweeten.html#fructose