The unreliable speed indication QRH procedure gives pitch/thrust settings in order to fly at Vls CONF 3 + 10kts.
If you want to insert your computed Vapp as a reference in the PERF page then, it is Vref (always = Vls CONF Full) + 16 + appr cor.
In your example, 115 (empty a/c!) +16+ third Headwind (if any).
Having said that...in an unreliable speed situation, you do not rely on speed indication anymore so fly pitch/thrust/config, should be more than enough!
The only use you could make of a computed Vapp is to compare it with your IR ground speed (corrected for wind and altitude) to check you are more or less flying at the correct speed range. It would be a sort of memo nothing more.