In your experience, how often do specialized barklice have difficult requirements in captivity? I assume they generally don't but just wanted to doublecheck w you.

The typical strategy is, first to provide adequate humidity. When in the field, I place psocids in jar with whatever the specimens were found on (dead leaves, twigs, leaf litter or green leaves with a patina of mold) and add a small piece of paper moist towel. I also take a small ice chest in hot weather to keep them from wilting in the heat. Usually nymphs (4th to 6th instar) will emerge as adults in a few days.

Some species are more difficult to rear than others, however.

This morphospecies appears more or less immune to heat and lack of air humidity given the highly exposed habitat, so I'm not too worried about that. Are the difficult ones all following a common pattern of difficulty or is it more of a case-by-case basis?

it is difficult to know what the nymphs are feeding on. For example on fresh green leaves (in spring) there might be no visible patina of mold or lichen, which many species feed on. Sometimes I make a dilute paste of Red Star baking yeast and paint it on coffee filter paper and dry with oven on low. Some species will feed on this material.

There are many different 'guilds' of psocids and each has is't own 'life-style' and feeding habits. The situation you describe is apparently unique. I would love to see some images of the habitat in which you found this species.

I found a nymph of the same morphospecies in a dried opened seedpod of a street tree (magnolia, if no other trees look like that).

Note that this isn't the exact location I found the psocodean, but it was nearby and definitely the same overall sort of habitat. I found mine near and in plants that were right next to the artificial slope (it seems to be illegal to go any further).

The soil surface was very dry at this time; numerous annual weedy native + nonnative angiosperms as well as dormant moss cushions were visible. There was also a considerable quantity of trash on the ground.

I did not check whether this morphospecies was specifically associated with the moths/Hesperoyucca or whether it was merely a generalist that was simply heat-tolerant and arboreal enough to survive in the crevices of the dead fruits. Also of note is that the grubs silk-glued seeds they were eating to the inside of the open fruit, preventing them from falling out as they naturally would. The silk had much larva frass in it.