You could try steeping the graham crackers in warm milk for a bit and then fat washing your bourbon in it. Some rrussels reserve or a knob creek single barrel may be a good call for this. They both have rich caramel and baking spice profiles that would lend themselves well to the graham crackers, as well as a rich mouthfeel for the silky texture that would pair up nicely with the vibe of the drink. Perhaps add some additional spices to the milk as well. Not sure what graham crackers are flavored with but I'm sure it's easy enough to find.

As for clarified coffee liqueur, agar agar or pectinex is your friend there. They both do a great job of clarifying liquids while mostly leaving the flavor alone. You may even want to have a crack at making your own coffee liqueur. I could see a nice medium-dark roast cold brew playing very well with all of this. Sweetened with Demerara or turbinado sugar to give it more hints of molasses to up the graham cracker flavor. You could even try bourbon as the base spirit instead of vodka or everclear to make an "all in one" sort of thing. High proof, fat washed, spiced, clarified coffee liqueur. Pour over ice, add some milk/cream and you're on your way!

This is giving me some ideas! Might have to try these out myself lol