Kweelo,
Firstly, do you qualify for transitional protection - are you within 10 years of 75's normal pension age of 55?
"The Government has offered transitional protection for all members of public service pension schemes who were within ten years of their respective scheme’s Normal Pension Age (NPA) on 1 April 2012. The Armed Forces Pension Schemes 1975 and 2005 (AFPS 75 and AFPS 05) and the Full Time Reserve Service Pension Scheme 1997 (FTRS 97) (Full Commitment) have a NPA of 55. This means that if an individual is a member of AFPS 75, AFPS 05 or FTRS 97 (FC) and was aged 45 or over on 1 April 2012 (i.e. born on or before 1 April 1967), they will remain in their current pension scheme and their benefits will be unaffected."
You will have served beyond your gratuity/IP point of AFPS 75 and beyond the FAFPS EDP point. As you say, you will get 28/30 of AFPS 75 benefits and you should also get tax free cash and EDP benefits from FAFPS (which involves a commutation also, at a rate of 12:1).
At 55, your pension will be increased by the retrospective and compounding effect of CPI since you left and when you reach your Deferred Pension age (67/68 for you?), your FAFPS annual pension will increase. At this point, you can commute some of your newly increasing annual FAFPS Pension to generate a lump sum.
Calculating your State Pension age : Directgov - Pensions and retirement planning