JAWS does not read the content of labels, and it always reports the combobox count as 0.

Combobox count:

The reason why it announces the number of combobox items as zero is that there is no real standard of reporting the number of items in a combobox. The reason why this works with standard windows applications is that JAWS detects if the combobox is a standard windows combobox, and with this information at hand it can deduct the number of items in a combobox. Probably the same heuristic is done against our accessibility implementation, but since the model we use slightly differs from what a windows combobox uses, JAWS does not find any items, and it will report it as containing 0 items.
That JAWS reports "0 items" even if the combobox is not a standard windows combobox is misleading and most likely a bug in JAWS. It should rather not report any count.
In order to fix this either JAWS must be fixed or we must know how the JAWS implementation is, and adapt our accessibility implementation to that.

Reading content of a label:

The reason why JAWS does not report the content of a label is probably because a label does not get focus.
However, normal windows applications also have this problem, for instance open wordpad, click "Format"->"Font".
You will notice that the label at the bottom is not reported.