I get my priors for my self-beliefs based on what's generally proven about human mental architecture. Your second sentence should be rewritten to indicate that you think we should take priors from somewhere beyond introspection.

I don't even think "priors" is meaningful as used. It's all just evidence to me. If there is some idiosyncratic personal prior belief in me, not due to evidence, I can either accept it (I do), or try to assume on faith that I'm like others except for this different prior, and adjust my prior until I match the conclusions of most people who use the same evidence as me. The question of where such a personal prior comes from is, however, unknowable until someone can scan my brain and explain exactly how it, in particular, works.

I generally distrust others' models of me except as it's useful to know what sort of impression I make. To get really useful insight about myself from others would require not only a tremendous competence and intelligence in them, but a huge amount of mutual trust and openness. Often you won't get honest negative feedback even if you ask for it. I see you have some sneaky tactics for getting around that.

I don't understand your "have I falsified this self-belief?". If I never have, fantastic. It must be true. If nothing I could have done (or that I can see other, different, people, do) would make it not true, then of course it's a pointless, tautological belief. I agree that you should be able to recall specific memories that are evidence for/against some believed tendency.