I was together with someone who was diagnosed with schizophrenia and her test result was INFP (even though i think she is ISFP with Ni+Se overdrive, as a result of having weak judgement, she has what appears to be Ni visions and tends to be a very active and adventurous globetrotter without much of a fear of risk of possibilities, which appears Se to me, she also loves to do garden work and similar handy things).
My father is probably ISTP and schizophrenic. Same setup, perception wise, technically.
Even though he is a very different character, due to different judgement.
What i see in both of them is that they compensate for the weakness on the 'psychotic stage' by being overly attached to the conformist stage. Being religious, seeking community, seeking a reliable world-view that can give worldly meaning to their lives, which seem so unreal to them, due to all the depersonalisation and derealisation that is involved in the 'psychotic stage'.
My understanding is, that the 'psychotic stage' is not the impulsive stage, but the ones before that.
It could be magenta (i think so) or even beige, i am not sure. I think beige is involved in autism.
It appears typical for characters to have a tandem-attachment to two stages that are two stages apart, there appears to be something like a muscial octave that makes all even and all odd stages resonate with each other, some stages are more communal in principle, some are more introverted. That would mean that if a part of you is stuck on the second stage (magic), it would be statistically likely that the rest of you gets stuck on the fourth (conformist) or sixth stage (pluralist). Due to that resonance.
What does it mean for Fi to be split? Well this is just intuitive way of conceptualizing any psychological conflict and what i was trying to say by that is that perhaps judgement (ego, which appears to encompass the dominant and auxiliary function) is somehow causing the problem. In my view a function contains the personal story. The unique differentiation. It's quite difficult to locate the whole story, it might as well be located in all functions. Well what i was trying to say is that there IS a story, that causes a particular developmental arrest (as opposed to the upper level of current development at a particular point in time). Arrest means, as i understand it, that a part in your memory (the overall structure within all functions) will, when activated by circumstances, activate a particular circuit between the functions, on a particular level of the functions, similar to a flashback. Suddenly you see red, so to speak. Your perspective is shifted to 'red' aspects of a particular stage, due to your storyline. Red for example. It's hard to understand if the perspective is guided by judgement, or perception itself.
I'm afraid i have no clue how to help with developmental arrest. From a purely objective perspective it could be seen like a complicated brain-damage. I mean imagine a fruit that is grown in a
funny way, a little bit mutated. You can understand it all you want, but that may not inspire change. I have developmental arrest too (i appear to have schizoid parts and i'm not sure where they are located in terms of stages) and i do crazy stuff with altered states of mind in the hopes of achieving change. But people are always like "don't even allow schizophrenic people to meditate, it makes it all worse".