It's the panic attack, not the premises, that's the problem. Lots of people spend time thinking about metaphysics and cosmology without making themselves sick.

Thing is, it sounds like the System 2 beliefs are justifying and protecting System 1 dysfunction. ("I should feel crappy, because the conditions of conscious existence are so fucked up.")

From what I can tell, people who have been in this kind of situation and have successfully gotten out of it have done so by fixing the System 1 situation — the reaction of panic, anguish, and despair — and not by adopting new System 2 beliefs. Things that reportedly help include guided meditation, cognitive-behavioral therapy, and guided use of various psychoactive drugs (ranging from antidepressants, anxiolytics, to various psychedelics in a therapeutic context, not in the wild).

In other words, this is probably not the sort of thing that can be fixed by reading the right philosophy or the right post on the web. Although it might disappoint Hermione Granger, reading the right book is not the solution to every problem. Rather, it is probably the sort of thing that requires the personal guidance of an experienced person in fixing the System 1 reactions that are causing you pain.