My (now ex-)GF's uncle used to be in the CF in the late 70s. He always told me 'exciting' stories about how he was Tpt WO (as a Sgt) of 2RCR and then was also sniper qualified in the Airborne Regt. All the 'qualifications' he told me about never added up but all I did was simply smile and nod. It wasn't my job to destroy his delusional reality and nor was it to inflate the delusional ego by asking questions about his Neverland.
Lateron, I have been in conversation with many ex-SniperJTFSecretSquirrels and 'I was on the design team for the M1 Abrahms' people that my routine simply is to ask a few questions like 'when did you do it?', 'what all did you do?' and so on. When they (inevitably) get to the 'I can't tell you about that' phase I apologise and play along a little while longer. When I can take it no longer or simply want to move onto more productive things in life, I ask him 'Well, with all the things that you have told me so far, won't that make you a target for kidnapping and subsequent torture for all the secrets you have in your head? You shouldn't advertise that you know something valuable if you don't want people to get it'. It may work for your issue, and it may not.