Hi Thomas,
For the first problem, I frankly don't know the answer. Probably the Up/Down navigation is not supported. A while ago, the SF team released a beta for a new Enhanced Listview which is much faster and has more features that the standard SF listview, but all population is done manually which may not be an issue with you.
Trent posted a sample application
here which will give you more details on how to populate the StrataListView. Be aware that some of the automation build in the standard SF listview are not yet implemented in the StrataListView.
For the second problem, you should be using one of the listview population methods instead using the Item.Add(). When the SF listview is bounded to a Business Object, some nice automation can be done like automatically moving the record pointer on the BO assigned to the listview, so when you navigate the listview you can make a reference to any property to its BO and you will be in the record that was selected in the listview.
There are many samples and thread about both listviews to help you compare with your code and use them as designed to take advantage of the whole SF framework. I love SF Listview, but when you need to load over thousand records, then the StrataListview will just fly over the standard one, performance is very noticeable.
Edhy Rijo