...I theoretically ought to answer “I can’t confirm or deny what I was doing last night” because some of my counterfactual selves were hiding fugitive marijuana sellers from the Feds. …
This seems easy to fix in principle. If, conditioned on the info that’s known, or that probabilistically might be known to your asker, your counterfactual selves were especially likely to hide fugitives, you ought to say “I can’t confirm or deny”; otherwise, you can be truthful, and accept the consequence that some negligible fraction of your counterfactual selves are going to be exposed. Of course, the frequency of being truthful depends on how much you’d care about being counterfactually exposed, compared to the counterfactual worlds where providing true info to the asker is beneficial.
This seems easy to fix in principle. If, conditioned on the info that’s known, or that probabilistically might be known to your asker, your counterfactual selves were especially likely to hide fugitives, you ought to say “I can’t confirm or deny”; otherwise, you can be truthful, and accept the consequence that some negligible fraction of your counterfactual selves are going to be exposed. Of course, the frequency of being truthful depends on how much you’d care about being counterfactually exposed, compared to the counterfactual worlds where providing true info to the asker is beneficial.