I will always love a game that lets you build a murderboard, and that's what the overlapping truths and lies remind me of here. I'm interested that the maps don't really refer to geography, too, but to structuring of information. Given it's hard to spend time with each other and physical items you have me wondering if it's possible to play this over online node graph sites, or mind map software? (I've played some excellent Microscope on Miro, as it goes.)
I'll echo the thoughts about playing cards that others have said; it feels like there's a lot of information on a card that isn't being used (rank, suit, difference from the card it's played on). If you just had a limited stack of index cards, that would provide the same limit on resources you mentioned earlier, perhaps? But I like your blackjack idea more; lots of little clues or two big ones, risk of endangering yourself if you overshoot, that sort of thing.
The Le Carre tone is strong; I like the way you could slot in other mission types easily; it's good. Thank you for the game!