How to consider diode leakage current in a voltage divider circuit
I think you are going to get a little disappointed with the BAS16 especially as the leakage value will slightly change with the measured voltage at the junction of R1 and R2 and temperature. I'd be more inclined to choose something like the BAS716. It has a typical leakage current of below 2 nA at 125 degC and a guaranteed max value of 50 nA at 125 degC: -




  I am not sure my above formula is correct


So, given the variabilities of the bAS16 (and also 1N4148 spin offs) I would say that your formula isn't accurate enough to be able to predict leakage across input voltage changes and temperature changes hence, the better choice (IMHO) is the BAS716 (or similar).

Yes, the forward volt drop of the BAS716 is higher but you can reposition its anode to the left of R3 and rely on R3 for limiting the current into your ADC pin. Then it comes down to what current is acceptable into the ADC pin under worst case considerations. My guess is that 1 mA is allowable and therefore you'd be fine.