If you have the patience and attention to detail / grammatical nuance to read the primary source pension legislation, it should be possible to calculate your PIA from first principles. I have succeeded in creating a spreadsheet that replicates the Pension Calculator figures for my own particular career circumstances, and use it to predict my PIAs - accurately so far! Doing so for the whole range of possible careers would be a huge undertaking and undoubtedly why those who’ve succeeded expect to be paid for their work. But if you boil it down to just your own case then it might be DIYable depending on your comprehension, maths and Excel skills.
If you want to give it a try, the AFPS75 legislation is
here (look mainly at Schedule 2 Part D and note that there have been several amendments since 2010) and the accompanying pension code tables are
here. The AFPS15 transitional provisions are linked from the first page.
In relation to the OP, I had a quick skim to see what might have caused the spikes in PIA; one possible culprit is commissioning, which at one point involved a transition period of 5 years on WO pension contributions (a large jump from Sgt?) and then a further jump to the officer pension. The relevant clauses have been amended during the period in question so this would be one to go through with a fine-toothed comb.