Leon,
Your calculations don't appear to take tax into account and a lump sum is hugely tax inefficient. A 40% rate tax payer will only get 42k in their bank (7k a year for 6 years RoS).
Also, the pay appears to come into effect 6 years after the start of phase 2 flying training; IOT plus a 6 month hold and you can delay all those figures by a year.
Has anyone seen anything in the AFPRB report about PAS retention? I have only skimmed it but it appears that they aren't concerned about retaining people after they've transferred to PAS (and are no longer in receipt of RRP)?