Hm. One thing that might disrupt the J/P dichotomy for me is the fact that I have obsessive-compulsive disorder, which may possibly make me more J than I technically should be.
Oh. Yes, that would throw things off. It's just like Asperger's or autism, in the sense that those blur a few types together (usually a combination of ISTJ, INTJ, and INTP).
*I cannot use a toothbrush or eat food that was touched by someone. My mother once accidentally used my toothbrush, and I then had to throw it in the trash (this is a trait I have observed to be more present in INTPs than INTJs. It may be a total coincidence, though).
I don't know. I get a little grossed out but find work around's for it.
With the toothbrush, I'm grossed out but am too lazy to buy a new one, so I just clean it as thoroughly as possible and once my head "knows it's clean," I am okay.
With the food, I cut off the parts that other people's lips touched, and then I'm okay. I could never eat the same part they did. I'm iffy on drinking out of the same glass as someone; I will use a [new] straw.
*I count random things obsessively.
No, I don't do that. It sounds OCD.
*I like to create large lists, hierarchies, and categories, and I enjoy hoarding much information. For example, if I plan on staying at a hotel in a location I have never been to before, I will obsessively research the location and the hotel itself to find out everything I possibly can. I will commit subway maps to memory, I will keep track of the precise number of restaurants in a 2-mile radius, all sorted by a quality ranking system, etc. In other words, I like to do things in a rather systematic manner. I can't tell if this is the J in INTJ, the Ti in INTP, or simply OCD.
I don't know either. My INTJ boss loves trains and will do all the stuff you are doing, but despite it being extensive, I don't think with him it's obsessive -- he just loves it, but he could choose to not do it, if it would cause undue hardship or he needed to stop.
The Ti thing does lead me into similar behavior, but not as much detail just to "control" what I am studying, what I am looking for is just indicative detail from which I feel I can truly understand something. So I try to collect various 'types" of detail that truly represent the topic/item in questions... at which point I get bored and stop.
I am the kind of person who methodically calculates things. The kind of person who selects the the most efficient walking route to school based off complex mathematical equations.
Ha, I do that too -- not the "complex equations" but an overall assessment of which is best. (Basically an interpolation/rough guess.) Sometimes I don't bother to follow it, if I don't feel like it, but I can get annoyed if people proceed to take the inefficient route after it is quite clear that the efficient route is the best.
So the tendencies are there, but I think I can more easily flex, compared to your descriptions. I'm annoyed, but I don't lose sleep afterwards over it.
When i was younger, I was less flexible. The practicalities of living made me loosen my grip some.