The next mistake was opening the door to solipsism and Brain-in-a-Vat arguments. This was so traumatic to me that I spent years in a manic depression.

Consider the possibility that the manic-depression was coincidental. When people have mental things happen for fundamentally biochemical reasons, they often misattribute them to the most plausible seeming non-biochemical cause they can think of. Exposure to ideas can exacerbate an existing problem, but it is unlikely that the lowest-hanging here has anything at all to do with the ideas themselves. Instead of looking at how you engage with stressful ideas, consider looking into other aspects of your life which might reduce your resilience.

With that said...

You started with a set of values and preferences and an ontology. When you encountered dust theory, you discovered that one of the definitions used to define your values - the notion of personal identity - wasn't fully coherent. You then tried to substitute a different definition in its place - an alternative notion of personal identity, which might not carry across a sleep/wake cycle. This alternate notion of identity is not the thing you care about. A small philosophically-minded portion of your brain has decided that it is what you care about, and is now in conflict with the other parts of your brain which don't accept the altered values. Listen to them; while those brain-parts aren't good at explaining things, they have knowledge and in this case they are right.