I can get you half way there..
For Level3 = 350, that's possible by just putting '='Total ' & Level3 in the "Label for Totals" box under Level2 on the Presentation tab of the properties.
For Level2 it's stumped me, because it wants to Sum up the quantity on Level2. I can't seem to get an individual label for each subtotal, it wants to put the same label on all?
Sorry I can't be of anymore help. It may at least give you a head start on trying to solve this.
Attached I've updated your qvw to show..
Hope this helps
Grouplabels.qvw 154.0 K