There's a number of problems with that XML I can see. You only have one vocabulary, but you're trying to put your second category into a second vocabulary. The <vid> tag should be 1 for both Teologia and Scienza. This is probably why the second product doesn't get imported because it's trying to be put into a category that failed to be imported properly. Or maybe it did get imported, and it's just hard to find.

There are several places where you have large structures in the XML tree without any data in them. You probably don't need to include them. <manufacturers> and <attributes> are the main things. And since there is a <model> tag directly on the product, you don't need to specify the one model in the <adjustments>.

Finally, it should be spelled <length_units>, not "lenght_units". The value of this tag should be cm instead of 1