Yes... I am having a difficult time considering the idea that outside studying may be necessary to do well.
It's funny, but I had pretty much the opposite experience. I found stats to be fairly shallow and easy to pick up, while I saw calculus as being very dense. I had an INTJ friend... loved calc and hated stats, just like you.
Yes. I think that's where the "I think I did really well on the test, therefore I bombed it" rule comes from. When you aren't aware that you have weaknesses and gaps in your learning, that means that you didn't review.
Gah... after doing some studying (yeah, I tried to STUDY. Not used to it, though, so I nearly fell asleep for the first hour before getting in the car, going somewhere else, walking around, and scouting out the perfect isolated spot in a dimly lit library corridor. From then on it took about 15 minutes to get into the zone, and from there I managed to study for 30 minutes before quitting) I figured out that the sort of mistakes I was making were, well, STUPID ones. I KNEW that you were supposed to break vectors down into components and that the two triangles were congruent, but what I didn't remember was which specific sides corresponded to one another. P ~ Q, or is P ~ Z? That's the sort of mistake that ruins a whole problem.
I suppose I hadn't done this sort of problem in over half a year, but I didn't really expect to be deficient or confused about it.